I got it

So I went to school today and only sent texts lightly yet by the time I got home my battery is at 15%. Any thoughts? Tips?
 
Make sure you have the latest updates. Firmware, HTC Software (read, latest supported version of Android), and especially PRL. An out of date PRL will kill your phone as it tries to ping towers that it shouldn't. If your EVO is "basically new," it might well have whatever the PRL was at its manufacture date, which would be old by now.

I have loved my faithful launch-day EVO, and will likely shed a tear for it when I trade it in on the EVO LTE.
 
So I went to school today and only sent texts lightly yet by the time I got home my battery is at 15%. Any thoughts? Tips?

Make sure you disable the constant sync of every thing on the phone. That's just a near-constant data connection. Also, make sure all of your radios are off that aren't in use, i.e. bluetooth, 4G, GPS, WiFi. And if you have WiFi at your school, I would use that instead of the 3G or 4G network. It uses a little more juice when you are actively using data, but when it's idle the WiFi uses very little.

Enjoy one of the best phones ever designed. I sure did. I liked it so much that I couldn't bear to part with it, or the accessories, when I upgraded.
 
So I went to school today and only sent texts lightly yet by the time I got home my battery is at 15%. Any thoughts? Tips?

LMAO!!! Welcome. now you sound like a evo owner lol. It's like having a Ferrari that gets 9 miles a gallon lol. I unfortunately have no advice other than buy another charger or extended battery on Ebay. I haven't found a tweak that works. Keep in mind it's still a Ferrari