Teacher vs. School Subscription?

What's the difference between the Busy Teacher and the Small School subscriptions? 

I teach PK-8 music and want to subscribe, but it looks like I'm limited to 400 total students with Busy Teacher.

I'm the only one who will use this subscription, but I teach 750 different students each semester. 

Does the Small School subscription also have the 400 total students limit?

What's the difference between 1000 private worksheets and 100/1T private worksheets? 

What's the difference between 100 workbooks and 55/1T workbooks?