You need a secret identity. Every hero does.
But what kind of identity? It needs to be one that doesn't interfere too much with your heroic career and that gives you enough time to actually pursue criminals without your absence being noticed.
Hmmm. Suddenly, you think about something your mother once complained about. Something along the lines of "these kids have too much damn time on their hands." You think she was referring to the crowd of high schoolers who always crowded the little coffee shop she liked to go to after work.
And that gives you an idea.
First, you make your uniform vanish. It doesn't fall off, it just fades away until your body is completely nude. Now you get a good look at how you've changed physically.
Yup, you have a lot of work to do. First, you need to be a least a couple of feet shorter. This is accomplished by just pushing down on your shoulders until your body takes the hint and folds into itself.
Then you mush your boobs down and press on your fingers and toes to make them thinner. And you rub on your skin to remove any wrinkles, since that would be a dead giveaway.
All that leaves is your face. You dig through a pile of old magazines that your mother occasionally picks up from one of the many spastic girls she works with at the local playhouse. You find one with a great big picture of a 17-year old teenager on the cover. She has a small button nose, a light dusting of freckles on her cheeks, thin eyebrows, and her hair in a ponytail. Perfect. This is the face you'll be wearing from now on.
Once the two of you look indistinguishable, you find your phone and start browsing. You need to find clothes and makeup. You also need to find a school to fake-enroll in.