Dress down day. what to wear!?!?

sooo tomorrows the last day of school and i don't have to wear a uniform tomorrow (y). i don't know what to wear! its gonna be 75degrees. and plus and i know how i should do my hair. i would straighten it but i wont stay ! help! and theres gonna be a lot of pictures taken so i have to look good(: please help me thanks*: