That is going to be your problem. Your choices are a good render time or quality lighting.

Kixum, that scene comes with a nice over head floresent fixture. Depending on how you import it; and I like it divided by mesh/shader as much as possable, the light will come in 2 parts, the fixture and the cover.

I used anything glows; it has problems with meshs some times but not in this scene, and a rather obnoxious render time. Now I have the version of this I was working on in a scene but it is a minimal lighting scene, after dark in the school and some kids that have snuck in to see the ghost teacher. So this is a new scene, moderate settings, and an hour render time.

Can you see the light I missed setting softshadows on lol