The president of the NASUWT teaching union is set to attack the government's education reforms, claiming they are distracting from the task of teaching children.
Mick Lyons will tell NASUWT's annual conference in Bournemouth hat education is being used as a "political football".
In a speech, he will say: "Daily denigration of the work and commitment of teachers, false claims of plummeting educational standards, and attacks on jobs, salaries, conditions of service and pensions are leaving colleagues heartily sickened and demoralised."
More top news
Labour strongholds tended to remain so - apart from a major loss for the party in Dudley.
Labour suffered a "terrible" defeat in Rhondda but has already won 16 Welsh Assembly seats as it looks to record a fifth term in office.
UKIP have made further gains in the local elections in the Anglia region and the Conservatives have won back control in Peterborough.