When I fit my kids I make them do a cartwheel and then stand up and not adjust if they don't stay covered I add inches. It's been pretty successful in preventing issues.
I love skorts so much, I've been using them for 4 seasons now. I love the look of traditional skirt but I hate girls messing with their uniforms or when the skirt sits above their butt and you just see spankies half the routine. I love how you never touch shorts but I'm not a fan of uniform...