Secondary school teachers are to ballot for strike action in a row over pay.

Their union the ASTI says colleagues hired after 2010 are being paid less for the same work.

Staff have also warned that they won't offer substitute teachers until the row is resolved.

Members are to be balloted on industrial action up to and including strike.

But ASTI general Secretary Kieran Christie, says the union will continue to discuss the issues with the Department of Education: