Short answer: bandwidth. Longer answer, a set of questions: * Do most teachers and/or students have sufficient upload capacity to send n-1 copies of their vide

Short answer: bandwidth. Longer answer, a set of questions: * Do most teachers and/or students have sufficient upload capacity to send n-1 copies of their video stream in an n-person chat? (A 20-person chat might be typical for a K12 classroom.) * Is it possible to do multicast across the Internet? I assert the answer to both questions is "no", so all the video streams need to go through a server/reflector. You're suggesting that self-hosting; a follow-up question: * Does your average school district have the bandwidth for simultaneous duplex video streams for every student and teacher? * Would they be able to acquire this bandwidth quickly? Also no. I've never used jitsi and don't know if there are other problems, but this one's a dealbreaker anyway.