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I'm not feeling the gray. I think the colors should be more vibrant - colors that reflect high schools: purples, red-burgundies, and blues. Anything but gray. The gold is fine - keep that.
I wouldn't recommend any drop shadows or gradients simply because it will make it harder to post to media that has a black background or another color etc. The shield throws me off. To me, it doesn't really say, "highschool".
I would get rid of the shield all together, enlarge the t-shirt and somehow, put it in the background of the text. And then outline the text with a think border, or use the well-known Highschool font.

Actually I just seen your older concept and it was waaaay cooler. More vibrant etc.