What is the best way to set up a group of accounts for an afterschool program?

What is the best way to set up a group of accounts for an afterschool program?  We have parental consent. However, we would like the accounts set up by grade level so we can monitor progress and support here versus 101 individual accounts linked to parent emails. We are not a school but we provide tutoring services from 3-7  4 days a week and on the weekends.