Virtual Conference Solution for Digital Learning

Hi,

I am looking for a virtual conference solution to my college for online tutoring. I checked TrueConf Server; It is slow though.
Have anyone used similar kind of software ?

We need multiple video conferences, it can be range from 10 - 100 or more in one conference. Screensharing, powerpoint share etc if any.
cloud based or self hosted ; both are welcome.

Thank You