Considering that christianity is purely a religious belief, not supported by any objective scientific realities, yes, that would be a completely inappropriate and immoral thing to teach or enforce in public schools. Fortunately, CRT (as well as the historical and sociological things you mentioned above) are in fact supported by scholarly and scientific evidence, and therefore are justified parts of a public school curriculum (or at least should be, if they aren't). If you are worried that some of these subjects are too advanced, then it should be simplified for younger audiences to make it more easily accessible to k-12 students, rather than ignoring it entirely. This similar issue was debated decades ago about teaching evolution vs creationism in public schools, of which religious indoctrination ultimately lost to science then too.