Steve Chalke criticised Boris Johnson for not have a strong enough plan for when pupils start a new term in September.
Boris Johnson has spoken of "a moral duty" to get all children back in class amid indications he would force pubs, restaurants and shops to close ahead of schools in the event of severe coronavirus flare-ups.
The Prime Minister is understood to favour only closing schools as the last resort after scientific advisers warned more restrictions may be needed to reopen classrooms in England next month.
Mr Johnson, writing in the Mail on Sunday, said it is the "national priority" to get all pupils back into classrooms in September after months without in-person education.
"This pandemic isn't over, and the last thing any of us can afford to do is become complacent," he wrote. "But now that we know enough to reopen schools to all pupils safely, we have a moral duty to do so."
He warned of the "spiralling economic costs" of parents and carers being unable to work, adding: "Keeping our schools closed a moment longer than absolutely necessary is socially intolerable, economically unsustainable and morally indefensible."
Chalke, who's the founder of Oasis Academy trust which owns 52 schools, told Premier Christian News he agrees that getting children back in the classroom is a top priority, but there's a huge lack of practical planning from the Government.
"We know that children need to go back, not just in terms of their academic learning, but in terms of their social and their emotional development. All of these things are very important.
"What the Prime Minister has been short on till now is the 'how'. There is no 'how do you do this?'
"The problem is that no school builder, whether they were back in Victorian times or a school that was completed last year, no designer, no architect, ever built a school that was 50 per cent bigger than it needed to be just in case there was a global pandemic and we have to socially distance. So we have a practical problem."
Chalke said there either needs to be a rota system for students attending classes or there needs to be more school buildings.
"In Waterloo where Oasis runs two schools… I got in touch with one of the local vicars who's volunteered to give us two church halls and a local hotel owner who's given us a floor and a half of a hotel. So that's my point. I agree with the prime minister, but Boris get practical."
He added that on Monday Oasis will be having conversations with its school leaders across the country about how they solve the problem in each of their community's because each locality is different.
Chalke also suggested that the government build temporary classrooms in playgrounds just as Nightingale Hospitals were built quickly for coronavirus patients.
"We don't know if there's going to be a second wave. We don't know whether there's going to be lockdowns, so it's no good just saying 'let's be open', we have to prepare to be open.
"What we should do is postponed the opening up term for two weeks so that we can use those two weeks with staff to get all the training in place, all the staff structures in place, and all of the technical bits and pieces in place to make this happen. "
Professor Chris Whitty, the chief medical officer for England, has warned the nation has "probably reached near the limit or the limits" of what can be done to reopen society safely.
Meanwhile, Professor Neil Ferguson, whose modelling led to the decision to impose the lockdown, suggested ministers would need to "row back on the relaxation of restrictions" to allow a full-time return to schools while keeping the virus under control.
