Boys/Guys always seem to be a problem.  The only advice I can give is to make it fun.  There are a LOT of distractions for kids these days between video games, computer, scouts, tae kwon do and other sports, etc.  Many just don't consider theater in their circle of vision.

What has worked for us is finding good directors who have done "kid-friendly" shows and having them do another kid-friendly show.  this was the kids say "oh, they're doing that???" but that puts a big strain on that director.

At our theater we are entering a unique era, in that one of our long-time actors is now overseeing the high school plays and musicals.... so there is a definite IN for the crossover talent.