period while swimming ?

this is less of a question and more of a story, but the pe teachers at my school make the girls go in the pool or participate in pe even when on their period. you have one day in the whole year to use your period as an excuse as to why you can’t participate. i was new this past year but i heard from a few friends that the reason they enforced those rules is because many girls who weren’t even on their period used it as an excuse to skip pe. i don’t think it’s right to force girls to use a tampon or get in the pool without one. maybe i’m mislead but i kind of think they are forcing girls into womanhood when they may not be ready for it ?? btw i’m 13, 7th going into 8th grade.