I don't disagree that it's important to tell/teach children that they are what they are and no one can make them what they are not. But teaching children this isn't the schools job, it's the parents job.
As for not teaching anything about sex at all from K-8? Uh, no. Starting in 5th grade kids need to be taught the biology of what is happening to their bodies - or what will happen within the next few years. Between 5th and 8th grade nearly every female will have gone through puberty, with the boys close behind in their bodily changes. Puberty and the biological function/mechanics of sex should be taught, as well as sex leading to pregnancy. After all that's what sex is primarily for . . . to continue the species. Anything else referring to sex -- religious beliefs, homosexuality, kinky stuff -- simply doesn't belong in the class room. The school's job is to teach the basic biology, not to teach about sexuality. That's what parents are suppose to do.