Overview
This article supports schools migrating from SIMS to Arbor via GroupCall in managing in-year timetable changes. It explains when a new timetable may be required in SIMS, why only the most recent timetable can be migrated, and how this impacts the transfer of lesson attendance data. It also outlines practical solutions—such as using Arbor-compatible software or making manual adjustments—to help schools manage timetable changes smoothly before and after migration.
Why is this important?
In-year timetable changes can significantly affect what data is successfully migrated from SIMS to Arbor. This guidance helps schools avoid data loss and timetable inconsistencies by clarifying the limitations of GroupCall’s API and SIMS data extraction. It also provides actionable steps to preserve attendance and timetable data, ensuring a smoother, more reliable transition to Arbor. For more information about what timetable data we migrate, see this guide in the Arbor Help Centre.
Importing a new timetable model into SIMS prior to your migration
Take our quiz:
Use this flowchart to help you determine whether your school’s timetable changes will affect the migration of lesson attendance and timetable data from SIMS to Arbor.
Have you made any changes to your timetable since the start of the academic year? (Click to expand)
✅ Yes
Outcome: Your school will be impacted, preventing some timetable and lesson attendance from migrating. Find out what impact it will have.
🤔 I'm not sure
❌ No
Do you intend to make any changes to your timetable before you migrate to Arbor?
✅ Yes
Outcome: Your school will be impacted, preventing some timetable and lesson attendance from migrating. Find out what impact it will have.
❌ No
Outcome: Your school will not be impacted and your timetable and lesson attendance should migrate in full.
You may be impacted if your school new timetable model has been imported into SIMS after the start of the academic year, with a timetable model start date set later than the original timetable start date at the beginning of the academic year. This is typically required when changes to the timetable model necessitate a new start date.
To preserve the structure of existing registers and any associated marks in SIMS, the new timetable is applied from a future date. This ensures that the previous timetable model—and its linked registers—remain intact up to the point of transition to the new model in SIMS.
How do I know if my school will be impacted?
You will be impacted if a new timetable model has been imported into SIMS after the start of the academic year, with a model start date set later than the original timetable start date. This is typically required when changes to the timetable model necessitate a new start date.
To check, review your timetable history in SIMS or speak to your timetable administrator. If a new model was imported after the academic year started, replacing the original timetable model, your school will be impacted.
See some examples below.
Examples of when a new timetable model would be imported
Here are several examples of when importing a new timetable model into SIMS becomes necessary due to curriculum changes:
Introduction of new subjects or qualifications
Adding new Courses, GCSEs, A-Levels, vocational courses, or enrichment options.
Example: A school introduces Psychology A-Level for Year 12 — new blocks and staffing need to be timetabled and imported.
Changes to subject groupings or banding
Reorganising how students are grouped for subjects (e.g. mixed ability vs. streamed sets).
Example: Year 9 Math's moves from mixed ability to tiered sets — new classes and teacher allocations must be reflected.
Alterations to the period structure or cycle
Changing the number of periods per day or the length of the timetable cycle mid-year.
Example: A school shifts from a 5-period day to a 6-period day — all lesson timings and structures need updating.
Staffing changes impacting curriculum delivery
New staff joining or existing staff leaving after the academic year has started.
Example: A Science teacher leaves mid-year — timetable is adjusted to redistribute their lessons across the department.
Curriculum model adjustments
Modifying block structures, lesson allocations, or teaching loads after the academic year has started.
Example: To accommodate increased PE hours, blocks are reshuffled and imported to reflect the new model.
Mid-year curriculum interventions
Emergency timetable changes due to curriculum gaps or performance concerns.
Example: Additional English support classes are added for Year 11 — new lessons and rooms need importing.
Specialist curriculum pathways
Creating or amending bespoke timetables for SEND, EAL, or alternative provision students.
Example: A new nurture group is formed with a tailored timetable — this must be reflected in SIMS.
What impact will it have?
During a GroupCall migration, only the most recently imported (active) timetable model can be migrated. Lesson instances from this timetable are used to match and store your lesson attendance marks from SIMS.
Unfortunately, previous versions of your timetable model cannot be migrated. This means we’re unable to match the lesson attendance marks that have been recorded in lesson registers that are linked to an earlier version of the timetable lesson instances. As a result, only lesson attendance records associated with your most recent timetable model will be migrated—any lesson attendance recorded prior to its start date will not be included. Please note: statutory attendance will migrate as normal and is not impacted by the timetable.
Example: Timetable Model A was set to run from 1st September 2025 to 24th July 2026. However, a curriculum change requires a new timetable to be imported, with a revised model start date of 3rd November 2025 (still ending on 24th July 2026). Any school migrating after this date will lose lesson attendance recorded between 1st September and 2nd November as it will not be migrated to Arbor, as it relates to the previously imported timetable.
What causes these limitations?
We use GroupCall’s API, which integrates with SIMS via the Xporter and Xporter on Demand (XoD) platforms. It securely extracts data—such as student, staff, attendance, and timetable records—using encrypted connections and structured scopes.
The data available through the API is determined by SIMS, who control which datasets are accessible to third parties. Due to limitations in the timetable data made available, only the most recently imported timetable model can be extracted via the API.
What can my school do to prepare?
We recommend that every school ensures they have a complete copy of the full year of lesson attendance and associated timetable data, including data from previous academic years if required, prior to their migration to Arbor. This ensures that your school will have access to historical data should the need arise in the future.
Due to the complex relationship between lesson attendance marks and timetabled lesson instances, there is currently no way to migrate this data through an alternative method.
Making changes to your timetable after your migration to Arbor.
If you need to make in-year changes (changes that take place during an active academic year) to your timetable after you have migrated from SIMS to Arbor, you will need to be using the correct Arbor-compatible software.
Use this flowchart to help you determine what your school needs to do.
Take our quiz:
Is your school already using an Arbor-compatible timetabling software, such as TimeTabler or Edval? (Click to expand)
✅ Yes
Outcome: You'll be able to import a timetable after your migration to Arbor, but you may need to make minor adjustments to your courses and teaching groups to ensure they are correctly aligned to your timetabling software before you can import a new timetable model. Find out more here.
🤔 I'm not sure
Outcome: Speak to your timetabling lead or curriculum manager to find out what timetabling software your school uses.
❌ No
Will you need to make any changes to your current academic year timetable after you have migrated to Arbor, but before the end of the academic year?
✅ Yes
Outcome: To make changes to your timetable in Arbor, you need to move to Arbor compatible software, such as Edval or TimeTabler. Find out more here.
Some manual changes can be made directly in Arbor - Find out more here.
If you need to make changes to your timetable that take effect the first day after your migration to Arbor, see information about how to import your timetable before your migration.
❌ No
Outcome: Your school will not be impacted but you should move to an Arbor compatible timetabling software as soon as possible before you can begin preparing your timetable for the next academic year. Find out more here.
Making timetable changes after your migration if you are already using TimeTabler or Edval
Once your school has migrated to Arbor, you may still need to make timetable changes before the academic year ends. If you're already using Arbor-compatible software, you can continue using it to manage future updates within Arbor as needed.
To ensure post-migration alignment between your timetabling software and Arbor, you may need to adjust your course or curriculum setup in TimeTabler or Edval. When courses and teaching groups are migrated from SIMS to Arbor, you might choose to revise naming conventions or restructure hierarchies to better reflect Arbor’s layout and functionality. Any changes should be incorporated into your timetable model before importing a new version.
Allow sufficient time after migration to complete any necessary administrative tasks before making further timetable changes. This helps ensure a smooth transition and avoids disruption to attendance tracking and curriculum delivery.
Making timetable changes after your migration if you don't have Edval or TimeTabler
Our school is migrating to Arbor over a half-term or holiday period, and our timetable will need to change from the first day back. What do we do?
If your migration is taking place over a half-term or holiday period and your timetable needs to change on your first day back after the break, you may be planning to import a timetable prior to your migration, to take effect once you have moved to Arbor. Unfortunately, we are only able to migrate the timetable that is active on the date of your migration and cannot migrate a new model that begins in the future.
Example: Your final migration is scheduled to begin on 24th October 2025, during the Autumn half-term, with completion and handover of your new Arbor MIS expected on 3rd November 2025. You plan to import a new timetable model into SIMS ahead of the migration, with a start date of 3rd November 2025.
However, because the new timetable’s start date falls after the migration begins, it will not be classed as ‘active’ in SIMS at the point of extraction. As a result, we will be unable to migrate the new timetable model.
Solutions
To ensure a smooth transition, we recommend moving to an Arbor-compatible timetabling software—such as Edval or TimeTabler—prior to your migration, to mitigate any potential blockers to the smooth running of your curriculum. If you are unable to do this in time, there are two alternative options available.
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Import your timetable before your migration
Set your new timetable to begin the day after your booked migration is due to begin (e.g. 25th October 2025 in the example above), and inform your Arbor onboarding manager so we can ensure the new timetable model migrates as expected. This will ensure that the new version of the timetable model is active when we perform your live migration and it will migrate to Arbor. Please note: This action will have an impact on lesson attendance. Find out more here.
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Make manual changes to your timetable in Arbor
You can make manual adjustments to your timetable directly in Arbor using the Timetable Administration tools provided. Log in to Arbor and go to: School > Timetable > Timetable Administration > Timetable Slots. Additional guidance for this area can be found here.
Please note: without compatible timetabling software in place, this process can be complex and time-consuming, depending on the scale and nature of the changes required.
Our school doesn’t use Edval or TimeTabler. What’s the best way to manage future timetable changes or prepare next year’s timetable in Arbor?
Schools migrating to Arbor will need to adopt a timetabling solution compatible with Arbor—such as Edval or TimeTabler—to build, manage, and update their timetable and curriculum. While manual changes can be made directly in Arbor, this approach is not recommended for long-term timetable or curriculum design and maintenance. Click here for more information about making manual changes to your timetable in Arbor.
Please speak to your Arbor customer onboarding manager for further information about moving to Edval or TimeTabler.
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