How can I play higher notes on trumpet?

I am in high school band and I would like some tips on how to strengthen my embouchre. I recently had my braces removed, which really changed how high I can play. I would like to expand my register and make high notes sound crisp and clear, but I am kind of struggling with it now. I can hit ‘em sometimes, but when I actually sit down to practice, nothing but air comes out. Any tips?