> Of course if you insist on acting like an authority and telling students that Newtonian Mechanics is "the Truth", then yes, you are lying to them. But you don't have to tell them that to teach them Newtonian Mechanics.

Do you think teachers really say "Newtonian Mechanics is the Truth" in class? Maybe it's different in the US but in Australia I've never had an interaction with a teacher like that.

Or is your issue that teachers are omitting that information? If so, that's quite a different thing to discuss.