When I was younger,at primary school,if you had forgotten your P.E.(gym) kit you had to do it in vest and pants 
Now,that was 15-20 years ago.Is it still the case or do they just make them sit out or provide clothes from lost property?I wouldn’t have imagined many schools sending especially older girls out onto a field or yard in just bra and knickers… 
I was a kid 25 years ago. If we didn’t bring our PE stuff, we’d spend the period sitting on the bleachers in our street clothes and get a fail for the day which affected our final grade if it happened enough.
Haj
We only dressed out from 7th grade up, but we played in street clothes and just had to be stinky all day.
Your gym uniform was a fairly large part of your grade for the day when I was in junior high and high school - you could probably only get about a 40% for the day if you participated but were wearing your street clothes. Each item was worth a certain percentage, so if you wore your uniform but forgot sneakers, you were docked ten or fifteen percent. You gym grade was just an average of all of your daily grades, so frequently forgetting your uniform would definitely hurt you.
Ironically, with gym periods being 40 minutes long, changing in and out of the uniform and taking attendance to see that we were all properly attired meant that we only had about 20-25 minutes for actual physical activity, although that usually meant dodgeball, anyway. (You can tell who went to my high school by their ability to throw long, low shots, because anything more than ten or twelve feet high ricocheted pretty sharply off the ceiling. And you had to be careful to avoid the poles in the middle of the room. Other than that, it was a fine gym.) On our really wild and crazy days, we did aerobics to an Elle MacPherson video.
We didn’t bother with the gym uniform if it was nice outside, because then we’d sometimes go for a walk around the neighborhood instead, for credit!
Like hajario said, don’t get dressed, sit on the bleachers and get a zero for the day…like I did my entire Junior year (circa 1985). Because I was such a bad-ass rebel. :rolleyes: