The proposal amended with Gov. Andrew Cuomo's recommendations on Friday prompted the powerful New York State United Teachers union to break off its cooperative relationship with the state Education Department.
The evaluations that could be in place this year would replace seniority in determining which teachers face layoffs.
Richard Iannuzzi of the New York State United Teachers union says the Cuomo proposals backed by state schools Chancellor Merryl Tisch on Friday will hurt education as well as teachers.
NYSUT had agreed to the Regents' proposal before Cuomo's additions.
Now NYSUT says Monday it is considering a legal fight to block the plan.