One dosing of sunscreen on the kids before they leave for school on a really hot day just isn't enough, even if it is a 50 factor.
As much as teachers are there to help, applying sunscreen to 30 plus kids who may have different skin conditions several times during the school day is more than some are willing to do.
So to give parents that peace of mind knowing that their child is well protected at all times, it makes sense to find a sunscreen that's small, compact and easy to use so that little ones can keep it in their school bag and reapply it themselves as and when they need to.