New York City taxpayers may have to pay up to $21 million in bonuses to thousands of teachers as part of a deal easing restrictions on public school class sizes, according to a new analysis released Tuesday. The powerful teachers’ union negotiated pay bumps of up to $8,500 in the upcoming school year beginning in September and $9,500 for the following year for educators in schools being exempt from the class size mandate. This was a concession to the United Federation of Teachers for agreeing