If I may make a suggestion: why block perfectly valid words like clitoris, cunnilingus, vagina, penis, anus, anal, fellatio, ejaculate, etc? I assume you do teach sex-ed at your school. Will kids taking these classes not be allowed to discuss these topics via email? Not to mention the sheer amount of well respected literature which includes these terms (and many other listed above)
In my opinion, filtering using a word list is a bad way to go to begin with. Instead, teach the kids to use proper judgment and good taste; that will be far more effective than any word list. However, if using a word list is a foregone conclusion, then I think blocking the proper and technical terms of genitalia is a huge mistake. It sends a message that our sexuality and our genitalia are something to be ashamed of and basically says that the school district's view on sexuality is negative. This is hardly the lesson kids should be learning. People need to be comfortable with their bodies and in control, not told it is a taboo and any discussion of it will be censored.
I wish your district the best of luck with this roll out. I used to work in K-12 IT, so I know just how insane and irrational "protective" parents can be.