Removing these books from school libraries is done with the understanding that the students won't otherwise be able to access them, i.e. they can't get to a bookstore or public library without their parent and their parent will also refuse to keep it at home. That is a de facto ban.
Now: you might happen to think that it's good that these books can't be accessed, which is something that can (and is) being discussed. But I don't think it's worth mincing words over what's happening, especially given that it's a standard (and non-partisan) use of the phrase "book ban" in the US.