The main issue there is the browser. A browser in a standard laptop is not able to render 51 videos at the same time. If you have a powerful machine, you can show 20-25 videos.
Regarding to server. A class with 51 participants means 2600 streams. In a 16 cores machine, this huge room can’t be managed (take a look to this performance test).
So I recommend you to design your system so not all students are publishing their video.
You can reduce the computational power reducing resolution, frames per second and bandwidth, but you will have to test yourself if the quality is ok for your use case.
Best regards