When we were little, we did the bath every Saturday night thing and then as needed in case of mud. About 5th or 6th grade it became every other day to daily depending on activity level and by high school it was daily.
My kids have always loved both baths and showers, so that was actually a punishment – to make them skip a day, or take only one shower in a day. My daughter, as an athlete, takes generally three showers a day, but one is more involved than the others. My son takes one a day but he hasn’t quite made the transition from little boy to full-blown teenager.
When I was in fourth grade puberty was still several years away, but nowadays there are 2nd graders having periods so hygiene can be more problematic. In any case, the teacher should never have told the kids that they stink. That was uncalled for.
In the case of folks with skin problems made worse by over-bathing, may I suggest sponging off with Cetaphil or an equivalent? That removes skin odors and dirt without drying and irritating the skin. I have both psoriasis and eczema and that is what I do, especially in the summer.