Having Nextcloud does not fulfill the actual needs of a school:
- timetables/class schedules
- provide information about homework
- possibility to inform school that a child is sick
- grades for the kid
- chat platform per class and between kids, teachers and parents
Nextcloud is for filesharing. But filesharing is not a priority need for a school. Yes, you can try to solve this via plugins and stuff. Bit this is just trying to bend something into shape that is not meant for the job.
Better to use a different platform actually tailored to the use case. For example edupage. But edupage has lots to improve (e.g. using in in the browser on mobile is horrible and the UI is very cluttered).
So I don't see how this actually benefits a school.