My high school was a public school in Kanto, and we were okay with it. But it depends on which school they go to even in Tokyo.
Although I wonder if Tokyo schools are more lenient with hair dying? My high school was in Kyushu but they were very strict about it, but my friend's school was a private school, and they were more okay with it.
By the way, are you guys going to watch C-ute's concert today? Don't miss it!