Apple classroom in macbook

So I work at a school and we try to use this app with our students but we've realized and don't know why is this happening, the app with the computer runs slower, some days don't work, I click in the classroom I created and nothing happens, I've tried closing it quitting the app to restarted and nothing seems to help, this has happened with a couple of teachers and only with the MacBook.

Is there are reason for that or something I can do to fix this?

Also, I've been using iPad to run the app and I have a question, when I connect devices to a class they will log in automatically when I go back to the classroom after I end the class correct? And each iPad can be enrolled into many different classes right? and they will connect to the specific as soon as the teacher's iPad gets near?