The Niagara Catholic District School Board has locked out elementary school teachers amid bargaining that began more than a year ago.

The board gave notice March 3 that teachers would be locked out starting today if no deal had been reached.

All central education unions — including the Ontario English Catholic Teachers' Association — have reached agreements with the provincial government to extend their current contracts until August 2019, past the next election.

The most recent round of bargaining was the first in a new system in which central deals are negotiated with the government then local deals are negotiated with the individual school boards.

Only three local agreements are still outstanding out of a total of 471, including the Niagara Catholic elementary teachers.

The teachers began a work-to-rule campaign Sept. 1, 2016, which the board says is adversely affecting students and their families.