The Boston Teacher's Union is declaring an impasse in their negotiations with the city on a new contract.
The talks have gone on for over a year, and the union is now asking the state to intervene.
The Department of Labor Relations will now bring in a mediator to help the two sides to reach an agreement.
This is the second time in the last five years that talks between teachers and the city have gone into mediation.
(FREDERIC J. BROWN/AFP/Getty Images)