I had old-fashioned braces, as did my two older sisters. We hated 'em but I’m sure our teeth look better today because we had 'em.
I rode the bus from first through eighth grade, when I was in public school. Never had any problems, and it could be fun hanging out with friends along the way.
I floss weekly at a minimum, and whenever I get gunk caught in my teeth (corn on the cob and Oreos are particular offenders). Every time I have a checkup my dentist encourages me to floss more often… but then tells me that my teeth look great.
I usually have three or four books going at once, and rarely have a problem getting back into a book if I read any of it in the past month. Longer than that, and I can see how it might be a problem.
My prep school had a swimming pool, and I was on the swim team. Practices were boring - back and forth, back and forth, yeesh - but meets were sometimes exciting. I lettered in swimming, but as a manager and not a competitor, in my senior year.
I don’t think any of my schools, at any time, had A/C. Maybe an occasional window unit.
This thread may interest you, then: High schools, YMCAs, and nude swimming