By Gary Eason BBC news, at the ATL conference in Torquay

Mr Knight said there had been "friendly disagreement"

English Schools Minister Jim Knight faced low-level jeering as he addressed the Association of Teachers and Lecturers conference.

One delegate asked how teachers could provide a good education to a class with 38 pupils.

Mr Knight said teaching assistants could make that "manageable".

He added that he had seen a maths class with 70 pupils "working very well".

"Class sizes are obviously something we take seriously," Mr Knight told the conference, in Torquay.

"If they are growing to the extent that the delegate talks about then there are some concerns attached to that.

"Teaching assistants and higher level teaching assistants working alongside teachers are very important to ensuring that class sizes of 38 are manageable."

'Perfectly acceptable'

During a backhanded vote of thanks to the minister after his speech, Phil Jacques of the ATL's executive committee said: "Class sizes of 38 should not be made to be manageable."

To cheers and applause, he added: "They just simply shouldn't exist."

Mr Knight told reporters later that he had seen a maths class of 70 pupils - with the room divided up by screens and three or four other adults assisting students in addition to the "charismatic" teacher.

"What I saw in Telford was perfectly acceptable. There was good learning going on."

You tell us what to teach. You tell us when to teach it. You tell us how to teach it and when to assess it Phil Jacques, ATL

Mr Knight also insisted the government did trust teachers and had made changes to the secondary curriculum in England and it was up to teachers how they delivered it.

Phil Jacques in his reply dismissed this.

"You tell us what to teach. You tell us when to teach it. You tell us how to teach it and when to assess it," he said. "What sense of the word 'trust' is that?"

He added: "The national curriculum is dismal, tedious, inflexible, of very little value to the great majority of children who are subjected to it.

"No wonder we have large numbers of disaffected children in those schools - in schools where the disaffection results in violence."

Afterwards Mr Knight characterised the exchanges as "friendly disagreement".