He should confront the school board and elected officials, or try home schooling if none of that works.
I've read pretty much every article that's appeared on FR about David Parker.
The real problem is that those who want public schools to double as indoctrination centers for (among other leftist causes) the "gay" agenda will brook no dissent - none whatsoever. And the aggressive promotion of homosexuality is first and foremost of the leftist agendas being force fed into children.
Mr. Parker's alternative methods can all pretty much be described as various appeasement methods.
In CA there is a law mandating K-12 homosexual indoctrination; from what I've read some school districts in conservative parts of the state don't pay as much attention to it as in the liberal areas. The actual alternative is finding a good private school or homeschooling. But a conscientious conservative doesn't want only their own children to be protected from lies and indoctrination; a real conservative doesn't want to see society go to hell in a handbasket.
The administration in this situation did not give Mr. Parker the respect that was due him as a citizen and a parent. It is clear that homosexual activists - not just the radical homosexuals themselves, but those who support their cause - are the most intolerant, vengeful, lying and powermad group of people we've seen in a long time.
Parents are a child's primary educators, not schools. The State can only justly overide natural parental rights if the parents are grossly neglecting their parental duties.