Headteachers have said they can't see summer schools during the holidays being used for educational catch-up as this must be driven by teachers before or after the break.
In an update to members, Geoff Barton, general secretary of the Association of School and College Leaders, said heads did not feel education would happen during the holidays.
"There’s going to be an announcement about summer schools – it’s got a head of steam behind it," Mr Barton said.
"You’ve got a whole series of people saying on behalf of the nation’s most disadvantaged children, something should be happening, it should be happening on school sites.
"Our position on all of that is two things: first of all the stuff that should happen if it’s educational should be driven by teachers and what that means is either before the summer holiday begins or after the summer holiday ends, it’ll be about teachers assessing where children are and deciding on their curriculum, and that is, as a principal referenced it yesterday, that’s not something we see happening in the summer holidays."
He added: "Part two is we don’t know quite what is being proposed and therefore I would strongly suggest is that we wait and hear what it is before we respond to it.
"I don’t think it would be a good position for us to be ruling out all kinds of activities taking place on some sites somewhere until we’ve heard them, partly because it makes us look like we’re on the argument of not wanting to support children and young people."
"That isn’t the same as us saying that you should be on standby, that you’re going to be working all through the summer holiday, we’re really not saying that," he said.
Yesterday, former Ofsted chief inspector Sir Michael Wilshaw said "good schools" would ask teachers to work over half-term, weekends and evenings to help disadvantaged pupils catch up and that summer schools would not be enough.
Details of the "huge summer of catch up" promised by the prime minister are set to be announced by Gavin Williamson this week.