Who's asking to impose anything on anyone except secularists wanting to impose secularism? It means not cutting it out of the possible things that might be discussed in any classroom. (Note that the idea that the only things that will be discussed in a maths classrom are maths is absurd.)
Actually, what evidence do you have that it is secularists who are wanting to impose secularism (by this you appear to mean anti-religion)? As I pointed out, as often as not, the complaints about religion in school come from people who are of the minority religion in an area. For example the Mormon and Catholic families in
Santa Fe Independent School District v Doe. Or a Jewish family suing in Utah,
Bauchman v West High School. Not to mention, "securalists" (by that meaning those that are anti-religion) are a small minority in the United States. In fact, it appears to be a majority of those in the US (even among people who claim to be Christian) that desire to keep public schools religiously neutral.
As for what is discussed in math class, I would hope that it is math discussed. Math teachers are hired to teach math, they can't even be asked about their religious beliefs as part of the hiring process, and there is no reason for religion to be discussed in math class.
But you still haven't answered my question, why do children need to be taught religion in public school? Is this not the parents right/responsibility? I personally find it amazing the number of Christians that complain about sex education being taught in schools (which was brought in because parents were failing) but then turn around and want the school to teach their religion.
Not to mention, what is so unworkable of a system that I described like the Mormon one? You can have classes that teach your religion, thus freeing parents from having to teach their children religion, yet not burden the public schools with it plus ensure they are taught by someone that is approved by the religion.
Again, the purpose of "secularism" in US schools is not to be anti-religious, as you keep claiming despite all the people pointing this out to you. Per official US government policies, schools are to be "religiously neutral" not "anti-religious". I won't claim that the government is perfect in following the policies, unfortunately people sometimes put their own agendas ahead of the law or simply make mistakes. That is unfortunate and it does end up being addressed. But the claim that securalism meaning anti-religion typically is put forth by Christians seeking to impose an element of their version of Christianity into the schools.