Had a similar pro bono assignment for a school overseas. Used a full frame with 35mm and 50mm lenses. The 35mm was very useful for putting context to the pictured and for candid shots of students doing experiments or teachers supervising students cleaning the grounds. The fast 50mm allowed me to do closer indoor shots with subject isolation to highlight what a student or teacher was doing.
Glad I wasn't asked to take photos of kids doing sports in the oval. I didn't have any telephoto that day.
Secret to getting great shots often? Take pictures often. Life's law of averages says increasing attempts at getting great pictures, you will eventually achieve success more regularly. In other words, there's ni substitute for going out, taking pictures, and evaluating one's work. Repeat the cycle.