The number of naturally occurring elements is usually prone to debate. According to stability, atoms are stable only up to the 92nd element – Uranium. Your teacher is correct when she says there are 92 elements that occur naturally on Earth. But when you carefully analyze each element, the elements Technetium and Promethium don’t have stable isotopes, and by its properties are extremely unstable with smaller half lives. So your text book might have discarded these two elements.