Wikispaces Classroom is a social writing platform for education. They make it incredibly easy to create a classroom workspace where you and your students can communicate and work on writing projects alone or in teams. Rich assessment tools give you the power to measure student contribution and engagement in real-time. Wikispaces Classroom works great on modern browsers, tablets, and phones. Wikispaces Classroom is free for teachers and students. They have over 10 million registered teachers and students on the platform.
Federally-Compatible TOS (link)
Privacy Threshold Analysis (PTA)
Privacy Impact Assessment (PIA)
System of Records Notice (SORN)
FedRAMP (CSP Package)