I think what's being described as "culturally relevant teaching" isn't CRT, but there is a degree in overlap with regards to some of the underlying ideas.
Critical Race Theory (based on the ideas of Derrick Bell) could be summarized as follows (Reader's Digest Version)
Racism is baked into all of the institutions of the US, and any proposed "neutral system" is just a guise for racial power since the aforementioned institutions were structured around white people, so any approach that upholds those existing institutions is still racism.
For example, Derrick Bell opposed the Brown v. Board of Education ruling for reasons of (I'm paraphrasing) "
removing barriers that prevented black people from being able to participate in the institution, is still racism because that institution was still tailored to white people, so allowing black people easier access to a white-centric institution isn't solving the problem"
What that idea boils down to, in practical terms, is the theory that any system/institution in which you can find a disparity in outcomes between white people and black people, is due to the fact that those systems were designed for white people.
So when schools propose things like lowering grading thresholds, or having different sets of standards for different demographics to alleviate disparity in outcomes... the are, in essence, employing ideas that are an outgrowth of CRT. (even though it's not through direct teaching methods)
But some actually are employing a more direct method of teaching some of those ideas.
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Like I noted before, there are cities implementing these in their curriculums (like Seattle and NYC...I'm sure there are others), and these recommended reading lists actually contain things from The 1619 project and some of the works of Derrick Bell.
So when people say "They're teaching CRT in schools", the defense of "No they're not, that's a college level course, nobody's teaching that", it's a bit of a semantics game... They may not be teaching the full in-depth college level content, but they're certainly conveying some of the ideas that are a subset of the subject.
Another analogy... Political Science and the study of the various political positions isn't (at least not any in-depth version) taught in middle schools. However, if a middle school civics teacher was adding books by Ayn Rand and Ludwig von Mises to the reading list, one could certainly say they're delving into that topic a bit, and injecting a certain viewpoint into it... and it would certainly be understandable if some of the parents accurately identified that there was a "pro-libertarian viewpoint" being promoted.