I know it was fairly recent, but I can't remember many details.

I remember kids at this school started getting powers, occasionally going insane and killing each other. (On a school trip a kid picks up a wooden sword and has a weird reaction to it, gains superhuman strength, and goes on a rampage.)

The gender swap aspect comes in because the class rep or whatever had the power to kill anyone that breaks the rules, this leads a gang of guys bent on overthrowing the school (I think) to use one student's powers (Basically pulls your dick off and you literally turn into a woman) to stay within the school's rules.

Thanks in advance; this is driving me nuts.

Sentou Hakai Gakuen Dangerosu