The invite button activates as you type, a comma or a space separates addresses, and an address you have already invited is quietly skipped.

A shared link never expires but dies the moment you generate a new one; an emailed invitation lasts seven days. What a student sees on a dead one.

Signing up as a teacher creates a student account beside it: one login, two separate libraries, and a switch that ends your other sessions.

Work done through a task link is recorded nowhere: the person sees their own result and the teacher sees nothing. Assign the task when you need the result.