I agree with all the exercises that Leftside provided. I'll add some more of my favorite glute exercises.
Supine body weight glute bridge - I like to use these in my warm ups, especially if you're working out after school and you've been sitting in class all day. Great exercises to get the glutes activated.
Barbell hip thrust - The best bang for your buck glute exercise. You can really load up the weight on these.
Single leg hip thrust - a little more advanced. The unilateral aspect adds some core stabilization to the exercise.
Lateral band walks - great for building lateral strength which is important for baseball players
Kettlebell swings - emphasize exploding the hips through and this exercise turns into a great one to build strength in the posterior chain.
Romanian deadlifts - same as above. Emphasize squeezing the glutes and getting full hip extension.