Ah yes, the argument that parents outrank schools. How does this work exactly? A parent that specifically wants schools to drug test or schools that assert their authority over that of the parents and not drug test.
If parents intend that their child not be subject to drug testing in private school, since they are paying, they can choose to send their child to public school or shop around for a school that permits drug taking.
It's not an argument, it's a fact. It is the parents job to deal with their kid's substance abuse issues. As you said, private schools can do as they wish and the parents can choose to send their kids elsewhere. In public shool. parents make their voices heard, the school board listens and carries out their desires. My system is being dumbed down due to this. It's a damn shame but the parents are letting us know what they want in an education for their kids. Fortunately, both of mine graduated before the neutering.
I don't know how much further LAUSD can be dumbed down. I am grateful that I have no children in school. Drug taking might be a prerequisite to graduation.