This isn't exactly a complaint but It's worth noting that these 'kids' are ALL old enough to be well out of high school (I believe Kurt is the youngest at 21) and in most cases out of college as well (Finn and Puck are nearly 30). This cast (if they could sing) would be more appropriate to RENT than GLEE. You can hide a lot with make-up and creative lighting but eventually it's going to show.
DeCarabas
This is not unexpected in high school movies and TV shows. It's very common to have actors in their 20s and even their 30s in these--so much so, that this is practically the convention now. For example: last year's Easy A and Beverly Hills 90210. And Ralph Macchio in all his Karate Kid movies...