I watch my childs swim lessons from a small viewing area, for her class there are 5 or 6 seats. Most weeks a mum with two older boys also sit in the area, both boys are on their phones, often so is the mum, the boys definitely don't watch any swimming. The boys go up to save seats before the rest of us have dropped our children off, class of between 6-8 so rarely can the rest of us get a seat and need to stand.
AIBU to think the boys should sit somewhere else. There is alternative seating away from viewing window and downstairs. Boys are probably 10/11 and 12/13.