Elaine Schwartz, who in 1982 co-founded the Center School, a public middle school in Manhattan, as a way to introduce bold classroom innovations, then remained its principal for four decades — long enough to see many of those innovations become common practice in schools nationwide — died on Monday at her home not far from the school, on Manhattan’s Upper West Side. She was 92.

Her daughter Andrea Franks said the cause of death was heart failure. Mrs. Schwartz had retired just a year…