As the parent of two kids in public school in New York, I can personally attest that John King was horrible. He pushed a high stakes testing regime whose only purpose seemed to be funneling money to Pearson. When parents complained at a public forum he hosted, he responded by refusing to hold any more public forums until he could change them around so nobody could complain at them. In short, the parents were responding to his changes with valid concerns (e.g. kids stressing out with tests so much they were vomiting on their papers) and he "addressed" these concerns by refusing to listen to feedback and doubling down on his failing strategy.
Sadly, once he left, Governor Cuomo has not only continued down the path John King was headed, but has made matters much worse. Cuomo's made it clear that he won't be happy until all public schools are closed and are replaced by business run charter schools (whose businesses contribute to his campaigns).