The article suggests this move could save the city $100 million a year, but that's not remotely its main thrust.
...half have disciplinary histories or unsatisfactory ratings, sources said.
Who am I to question that? After all, sources said it. Nonetheless, that also means that half don't have disciplinary histories or unsatisfactory ratings. So there are 50% of your ATR teachers that, if the article is to be believed, could be placed immediately with a $50 million savings for New York City. Let's take a look at those other scary teachers:
25% committed wrongdoing, 25% received an “unsatisfactory” rating, 40% worked in schools that closed or downsized and 10% teach subjects that are no longer offered in schools.