I’m still a little confused on this, are you saying that the typical schedule for freshman at your hs is 5 core, 3 electives, PE and then a lunch in there somewhere, so like 10 potential time slots if you max out on the electives? That sounds like a lot. The electives are not going to make or break for admissions imo, in CA high schools or at least most in bay area, you only have seven or eight slots, and if you’re playing a sport, the last period has to be free for practice, so basically six classes, one or two electives max and you have to take Art for the UC/CSU requirement and PE is mandatory in 9th grade.
The issue you could have is if the hs offers a lot of electives and you son has four years of three chorus classes, when maybe other kids are using them for a second foreign language, or computer science or business to stretch themselves. Adcoms could question the intellectual curiosity but I cannot believe they’d get into that level of detail.