I've done this lots, never gotten in trouble for it!! Cody has had midnight blue hair, green hair, red hair, burgundy hair, purple hair, bleached hair ... the list goes on with him! Jenna has also had red hair and bleached hair, and Xander, when in preschool, had a green or red mohawk!!! Thankfully, the schools here are laid back.
Currently, Cody and Jenna (and her best friend) are now sporting fuschia pink and midnight blue streaks, done tonight, by my neighbour. This is on top of Cody's two shades of blond, two shades of red and two shades of brown streaks he has had done this summer.
I'll be taking pics tomorrow of their first day of school to share!!