Many academies and free schools are currently selling themselves on having “small class sizes”, but, looking into my crystal ball, I wonder whether we will be seeing big class sizes in many of these schools in the future. This thought arises having spoken on the Vanessa Feltz Show on BBC London this morning about Sutton Council who are asking the government if they can increase their class sizes to 32 from 30 because there’s a rising birth rate in the borough and not enough school places. The DfE responded to an inquiry from the Feltz show by saying that free schools and expanding popular schools will be the answer to this explosion in the school population. They indicated that 30+ class sizes was not acceptable and, in fact, illegal. This is certainly true for maintained schools.
But I’ve checked with an academy and they told me that their funding agreement means that they can have whatever class sizes they want as long as they meet health and safety requirements. One SLT member told me that he could quite easily envision the situation in a few years time whereby you might have very large classes (ie 40+) in academies, provided there was the right accommodation. What you could do, he said, was have one main teacher, properly paid, and then have teaching assistants on a minimum wages helping to keep order. “You’ll hire in a few heavies on a cheap wage to keep the kids in line and then get a good teacher to take the class. That way you’ll save a lot of money on wages, and you could also say that the teacher-pupil ratio was good to the punters when, in effect, it really isn’t,” he chortled somewhat ironically: it isn’t anything he wants happening in his school, but he knows of schools where it might. This is, no doubt, what will happen, and may well be already but we simply don’t know about it because academies and free schools are not accountable or transparent in the way LA schools are.
No wonder Sir Michael Wilshaw is calling for Local Commissioners to keep an eye on these schools!
talesbehindtheclassroomdoor 
Alternatively, an Academy with freedom to depart from national pay scales for teachers could have small class sizes by having more teachers on lower salaries instead of the teacher + TA combo. Some teachers might find the trade-off between salary and reduced workload attractive.
This is something that non-academies could also do, if they were able to placate the unions locally – eg by employing a large number of Higher Level TAs and using them to teach classes regularly rather than as an exception.
It might be a way for poorer perfoming schools which had excess space to improve themselves – small classes would not be an option for schools that are already at the edge of their physical capacity.