Our area has several options for youth community theatre. It's possible to be in several musicals and plays year round just using that option. They (the youth community theatre programs) tend to draw the kids that are really, really interested in theatre and who also participate in their schools' programs.
As far as school productions, the private schools have some of the better productions around here. The boys-only schools have openings for girls to be in their shows, and vice versa with girls' schools looking for guys. Again, that draws in the students from all over the metropolitan area who are really, really interested in performing arts.
The local community theatre scene is pretty vibrant overall. Aside from established groups that have been around for years and years, there's a new group that focusses on giving opportunities to college-age and mid-twenties for directing, choreography, lighting, etc. Most of their roles go to college kids, but younger dd snagged a couple of roles in the past few months, including one that she didn't audition for -- they contacted her and asked if she could take the role. Overall she's been in 4 musicals in the past 9 months, plus one ballet. I'm enjoying the break right now where we aren't involved in any shows!