1. "Elementaries" as the plural of "elementary": This spelling is correct when referring to multiple elementary schools or things related to elementary education.
2. "Elementaries" as a word in its own right: There's no word in common English usage spelled "elementaries." Perhaps you're thinking of a different word, or you may have made a typo.
To be sure, it's helpful to provide more context! What are you trying to say? For example, are you talking about elementary schools? Or are you referring to something else entirely?