Why not both ?
They may "trim" playing fields, build houses, much cheaper than moving a school.
There's also small bits of money to be made from more aggressive marketing of the facilities during holidays and weekends.
But if I was tasked with running a school for British parents, then I'd look at what they want.
I believe that there is a strong demand for after-school care, and for earlier supervised playgrounds, (say from 7:30). This could be marketed as various after schools clubs and tutoring.
Most schools have a little bit of this, but I'd be tempted to see what falls out if you do it with gusto and money.
Rather than go home to sit in front of video games and DVDs, your kid can learn to cook, build model trains, or do archery.
I suspect that you might hit a virtuous circle where not only was this a profit centre, but your school would quickly gain a reputation for supporting kids interests.
Staff might not be wildly happy about doing this, but it doesn't have to be the academic staff, indeed it might be cheaper to use less qualified folk.
Combine both these ideas, and do your own summer camps as well.
British parents work the longest hours in Europe, I believe that they'd not only pay, but in some cases thank you for the service.
Or not, I'm no expert in schools as a business, but you don't win in a competitive market with a dull low value product.