Jeremy Corbyn has recieved a standing ovation from teachers as he condemned government plans for all schools to become academies as "the asset stripping of our education facilities".
The Labour Party leader, who became the first leader of any political party to address the National Union of Teachers' conference in living memory, pledged that Labour would support the union's campaign to oppose the plan.
Later in its weekend conference delegates are expected to back an emergency motion warning of industrial action if the Government goes ahead with its plans - which would mean 17, 000 schools -mostly primaries - becoming academies by 2022. A one-day national strike is planned before the end of the summer term.
In his speech to the conference, Mr Corbyn, who said he was the first Labour party leader ever to address the conference, told teachers: "This is an ideological attack on teachers and on local and parental accountability - an attack which was nowhere in their manifesto at the last general election."
As part of the plan, the Government ssid they intend to scrap legislation whereby all schools have to have an elected parent representative on their governing boy.
Mr Corbyn added: "The Tories want to shut parents out of having a say in how their children's schools are run.
"I want schools accountable to their local communities - not to those pushing to be the first in line for the asset-stripping of our education facilities to be handed over to somebody else."
Mr Corbyn, who was greeted with cries of "hooray" from teachers and given a standing ovation even before he started speaking,, said he had "very real fears" about the intentions of the Government and "those who pay these exorbitnt salaries to run academy chains". Some chief execuives have been paid in advance of £250,000 a year. He was given another standing again as he finished his speech.
He said the Government should instead be tackling the current "crisis" in the education system. "Children are facing rising class sizes, there is a shortage of teachers and parents already face a crisis in school places..
"The forced academisation will do nothing to address any of these problems. And yet £700 million will need to be found to fund this needless organisation that fails to address a single issue that matters to teachers, parents or pupils."
He said that school budgets were being cut in real terms for the first time since the 1990's, adding: "The pressure of work forced more teachers to quit last year than ever - over 50,000 - and the Government has now missed its trainee teacher targets for the last four years in a row. That has resulted in half a million children now being taught in classes of over 31 in primary schools.
"One in four staff are increasing their use of supply teahers, one in six are using non-specialists to cover vacancies and one in 10 are resorting to using unqualified staff to teach lessons.
"Labour will work with you, with parents and pupils, with local authorities and our communities to defend education and stop these plans for forced academisation."
Mr Corbyn's speech, the first time a senior Labour party member has addressed the conference since then Education Secretary Estelle Morris was heckled in 2003, comes as the union is squaring up for a battle with the Government over the proposal.
Union leaders said that Mr Corbyn had asked to come and address the conference - and its executive had supported the idea without a dissenting voice. It said the executive would also consider any similar request from Prime Minister David Cameron but could not say whether that would be agreed.
It is expected to debate an emergency motion over the weekend which will warn of industrial action over the proposals. Kevin Courtney, the NUT's deputy general secretary, warned there could be "many more disputes" because the plan would mean scrapping national salary scales and allow schools to set individual salaries for their teachers.
However, the union is confident it will win support to defeat the plans in Parliament - as many senior Conservatives in local government, including Oxfordshire - where Prime Minister David Cameron lives - have spoken out against them.
It has gained another unexpected ally, the right-of-centre Conservative think-tank the Bow Group. " Hector Marchetti, speaking for the group, said the plan followed "a worrying trend in recent years to further centralise decision making from local communities". This was creating an "ongoing ideological drift between the party snd conservative values".
As the plan was not in the Conservative manifesto, the House of Lords- which will be targeted in the union's campaign - is free to throw them out.
Delegates will also debate another emergency motion calling on the Government to cancel all primary school tests this summer - on the grounds that teachers have not been given adequate time to prepare for changes to them. Currently primary school pupils face baseline tests when they first start primary school ate the age of four, a phonics tests at six, an assessment of their spelling, grammar and punctuation at seven and national curriculum tests for 11-year-olds in reading, writing and arithmetic.
A survey of over 5,000 primary school teachers by the union revealed that 96 per cent thought the spelling, grammar and punctuation tests in particular would cause too much stress as much of the material was "too advanced" for seven-year-olds. A similar percentage thought the same was true of tests for 11-year-olds, Only one per cent disagreed.
Christine Blower, the union's general secretary, said: "The findings of this survey are shocking. Any responsible government would sit up and take notice of what primary teachers are saying."
The Department for Education says the tes help reassure parents their children attain literacy and numeracy levels before they leave primary school. Growing numbers of children were becoming fluent readers, in particukar, because of the phonics test for six-year-olds.