First of all, registering takes few seconds with twitter/github. Secondly, it's not a must. Only you can register and share the collaboration URL with your 100

First of all, registering takes few seconds with twitter/github. Secondly, it's not a must. Only you can register and share the collaboration URL with your 100s of students. They can collaborate if they want to, or you can teach them in "Teacher Mode" - registration is not a must! Hope that clarifies your doubts :)