I don't know of any gender-specific scripts, but i've read about secret languages that are taught as part of a boy's initiation into adulthood in, i think some Pacific island cultures. I can't find a reference to any of them, though - just too secret, i suppose.

I did find this, a secret language spoken by traditional healers in the Andes:

https://en.wikipedia.org/wiki/Kallawaya_language