The problem with CRT is that it is not just an overview of racism or lingering systemic racism for educational purposes. It's indoctrination and conditioning. The kids are pressured to live and think a certain way and to put it into actual practice in their lives- to go home and fight with their parent and call them evil, to snitch on family so they can be canceled, to vote a certain way, to dedicate themselves to servitude to minorities, and so forth.
In other words, critical race theory is praxis, not just theory. The teachers groom kids to behave and act a certain way, and many parents are not happy about that.
If I haven't made myself clear, think of being in a religious school as opposed to learning about religion. Learning about religion means you simply learn the origins of a religion, what it's core beliefs are, and so forth and you are NOT expected to follow that religion. However, being in religious school goes far beyond that and you are supposed to actually practice the faith. You have to pray, attend mass, go for confession, follow the rules of that religion...or else you get punished in various ways.
Zealous crt teachers are quite adamant about the punishment aspect. Kids get sgamed, get told they are evil, parents are threatened with meat campaigns to get them fired...
So what are some things that CRT teaches?
It purports that white/ethnic European people are always the oppressors and always racist, and that everything is white supremacy. PoC are always victims and cannot be racist. So european/white kids are brainwashed to believe that they should always ally against their own, I they are in any altercation with a poc it means they are racist, producing white children is evil and perpetuates white supremacy, they should support affirmative action and reparations and contribute to that by not hiring for their own kind and hiring poc instead, they should pass on promotions at work so that poc may have the promotion instead; if they are an author/filmmaker they should dedicate their tale to to writing about and representation poc instead of their own white kin, etc.
In other words, if LeBron James beats up a homeless white veteran, the homeless veteran was the oppressor in that situation.
That is CRT.
It's not just merely teaching, it is praxis.