I believe I read this in a study from the Barna Group, although I can't find the source.

They found that young Christians who went to a church with a less-structured program for youth were more likely to stay involved in church and active in their faith through their 20s.

Kids who attended churches with stronger programs were less likely to report positive faith measures into their 20s.

I see two interpretations to this study: first, that churches with strong youth programs may undermine spiritual development; second, that churches with strong youth programs draw in more fringe participants who wouldn't tolerate going to a church with a weaker youth group and are less likely to stick with their faith into adulthood.