As a teacher I want control over what my students do online. Most sites allow users to create accounts using the gmail hack of email+username@gmail.com where the email is the main email account created by the teacher, and the username is each student. Most recognize this as separate emails, but all of the contact info goes to the teacher's account. Also, at the moment, my students do not have school emails so unless your site could accommodate this, I cannot use your site, which is a sad thing : (