Opposite where the blackboard would have been were three stacked platforms with theatre seats on them.  Behind the top platform was a wall  with a window that formed the sound/light booth.

 

The ceiling had a small grid for lights to hang.  Obviously some electrical modifications were made.

 

The room was approximately your room's size.

While there are technical aspects to address, a change in use or occupancy of a space can also involve code and accessibility considerations.  You might want to talk to the appropriate party at your school or district to see what impact this may have in terms of exiting, accessibility, life safety, etc.  It sucks to get all excited about such a project and spend significant time on it only to later discover that major changes or costs (additional exits, sprinkler systems, ramps or lifts, signage, assistive listening systems and so on) are necessary to address compliance issues, it's usually much better to know the situation as soon as possible and be able to maybe work that into your plans.