First, a player shouldn’t play for another team until his high school season is over. If I was coach and the player got injured I would be steamed.
Second, my kids are 29 and 34 now. Rules may have changed. But when they were in high school in PA there were a couple of Team USA athletes at our high school. They had to get PIAA waivers to play with Team USA while their seasons in that sport were active.