NASUWT general secretary Chris Keates said the teaching profession is in "crisis" following "three years of attacks by the Coalition Government".
Teachers' unions have announced a rolling programme of regional strikes over the next few months, affecting schools across England and Wales.
It is thought the action could be followed by a national walkout in the autumn over a dispute on pay, pensions, working conditions and jobs.
Education Secretary Michael Gove said in a letter to both unions in March that he was wrote willing to meet them to discuss their dispute, but also insisting that the "direction of travel" on both of their key issues is "fixed".
From this autumn, teachers' pay will be linked to performance in the classroom, with schools setting salaries, rather than following a national framework.
More than 2,500 schools in the North West of England could be affected today as teachers stage a walkout over pay, pensions, working conditions and jobs.
Members of the National Union of Teachers (NUT) and NASUWT will take part in a strike, the first in a planned national rolling programme of strikes across England and Wales which will continue in the Autumn term.
Twenty two authorities, and a possible 2,765 schools, across the North West will be affected as joint rallies are held in Liverpool, Manchester, Chester and Preston.
Chris Keates, General Secretary of the NASUWT, will address the rally in Liverpool at midday.
The National Union of Teachers (NUT) and the National Association of Schoolmasters Union of Women Teachers (NASUWT), the biggest teaching unions, are gathering for their annual meetings where they are expected to speak out about pay and Ofsted inspections.
Education Secretary Michael Gove could face another vote of no confidence following a similar move by the the Association of Teachers.
But, according to the Telegraph, Gove is refusing to bow to pressure over the demands of unions, saying “the direction of travel is now fixed” over teachers’ pension and pay arrangements.
The NUT and the Nasuwt have already announced joint strike plans.