iPrism airplay issues

I'm using my apple tv and ipad in my classroom. I am having an issue with airplaying video. I can mirror most things but if I try to airplay a video clip, I get an error message. I cannot get all my apps to load on the apple tv home screen as well. I am using wifi and have been able to enter the wifi password. We have an iprism login but I cannot find where to enter that info. Does anyone have any idea to fix this?