Oh, everything! Getting to work with kids (!!), getting to learn from very experienced teachers, the community (my coworkers and I really did feel like a family), the opportunities to do office work, my wonderful boss - EVERYTHING! This is the perfect internship if you are interested in Theatre Education.
What I wish was different
Honestly, nothing! It was a rarely perfect experience.
Advice
I think my advice would be to take advantage of the variety of age groups you are allowed to work with. Try to be open-minded about working with different age groups. We were given the choice to choose which age groups to work with, or to just be flexible and take whatever we were given. I chose the latter option, and therefore got to work age groups I had never worked with before, which was honestly invaluable for me.