Labour says children are being crammed "like sardines" into "super-sized" school classes, as it focuses its general election campaign on education.
Jeremy Corbyn said 40,000 primary age children were taught in classes of 36 or more in England in 2016, blaming "broken promises" by the government.
But the Tories said the Labour leader's comments were "a massive own goal".
They said the Labour-led Welsh government had overseen increases in class sizes in Wales.
Meanwhile, Lib Dem leader Tim Farron is to target Conservative MPs who backed…