You may have to get a schedule since they will often have duties they have to do such as on Monday they do daytime recess but on Thursday do afterschool yard and bus. Some do sports and clubs after school - especially if you have high school teachers. Schools here have staggered start and stop times so they can double up on buses so it will vary. Some prefer to stay at school and get their marking and lesson planning done instead of taking it home so you will have to make sure they understand what your expectations are and the penalties and responsibilities.