It is never too late to start at all! As for the high school team, get the info on it first. Many high school teams for gymnastics are walk-on, it all depends on your school. Some schools take it very competitively while others let beginners join with no problem. My school has tryouts and they do make cuts, but my friends school team is walk-on and they took people with little to no experience. So for sure you should find out the information because it all depends on what your school requires. You are certainly not too old to try gymnastics. Last week I had two 15 year old girls join my class as complete beginners! Good luck!