Window STC

The STC 35 requirement applies to exterior windows. Interior windows would need to be accounted for in a composite STC rating for the interior wall and window assemblies combined.

would STC 35 apply to exterior doors?

Would interior doors be accounted for in the composite STC rating of the assembly? (most doors have a stand-alone STC rating).

ANSI S12.60 isn't very clear on this. In 4.5.3.1, the standard says that a composite rating including the doors should be made. Later in 4.5.5 the standard says that classroom entry doors should have a minimum STC 30 rating and music room doors should have a minimum STC 40 rating.

I would say that if a classroom has a single, standard-sized door opening, that the standalone ratings outlined in 4.5.5 would be sufficient. If the classroom has multiple door openings or if the doors are oversized, that it would make sense to make a composite rating. For doors located between classrooms, a composite rating would be appropriate.