Our public school system implemented a dress code 5 years ago. Solid color, collared, sleeved shirts that must tuck in with arsm raised; black, navy, khaki slacks or blue jeans which are plain and must fit, bells no larger than 2/3 of your shoe; belts etc.. No logos larger than 2"x3". DD12 likes to wear hoodies, but finding hoodies that don't zip (no zipper; too easy to hide things) with no logo proving to be harder than expected.
School switched to dress code when she was in 2nd grade and her sister, DD9, has only known dress code. They are okay, but bored with. Interesting to see what styles they come up with. Thank goodness the polos with different little critters are popular right now!