Newtonian physics doesn't just work well enough for education. It provides an incredibly accurate and precise model of the world except at extremes. The majority of engineering does not necessitate using theories of relativity. Both theories are incomplete models approximating reality and are very far from being false.

True and False in general communication means based on best available evidence and expertise statement contains no obvious contradictions or falsehoods based on an optimistic parsing of meaning language and intent. Notably this leaves out misleading or missing data because those concerns are separate from truth and falsehood.

E.g. if I say the earth is round we optimistically parse round to include oblate spheroid and rate it true.

If I say that the earth is flat we rate it as false because there is no reasonable interpretation possible other than confusion or malice.