If you have students who come from other schools to attend your clubs or childcare, you can log their attendance in Arbor.
Students must be enrolled in your school to be eligible to attend clubs. In Arbor, students can be enrolled in your school without attending classes and appearing in lesson registers. All you need to do for your external students is follow the instructions in this article: Adding guest students and changing enrolment modes
Once you've done this, you can manually register your guest students for clubs, trips etc and take attendance for them! As clubs don't contribute towards your statutory attendance, their marks won't affect your figures.
You can see more on how you might want to use this for wraparound childcare here: Wraparound care - Setting up a breakfast club or after-school club
Please note that adding guest students can skew your report numbers. For example, they will be included in your school Dashboard Statistics and could be counted twice on the MAT MIS if they come from another school in your MAT.