The first thing that I noticed is that you said that your demographics target ages 15 to 24. From the perspective of advertisers, this target age group (teens and college students) don't have much money - and they're certainly not big budget spenders with lots of discretionary income. I think this is a big reason why you're not able to pull in higher CPM rates ... it's simply not worth it to many advertisers to spend a lot of money targeting this age bracket.
Keep in mind that many AdWords advertisers (the advertisers who appear on your AdSense) are products and services for sale. You may have better luck selling inventory yourself to content sites who make money selling advertising (such as DaniWeb) where the site visitors don't have to shell out big bucks.
cscgal
The Queen of DaniWeb
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