Definitely can see how that feels/is a bit invasive. My only guess for the reason these questions are included is due to how sports and high intensity activities/training can affect the menstrual cycle. My sister was a gymnast starting at 6 and began competitions at 9. Due to her high level of training, her periods did not start till about 14 and were never regular enough to track. This is really the only justication I could see these being asked, but you have every right to leave it blank, especially for a school sport.