I had a tutor for my daughter when she was going to sit the grammar school entrance exam. All her friends went to the Explore Learning up at Sainsbury's, you know the one I mean. Our tutor was strict, a ex school teacher and very clever and passionate. She's in Hale Barns, probably not far from you. The Explore Learning staff were barely out of high school with no teaching degrees, more glorified babysitters.
Explore Learning was apparently loads of fun. Our tutor was hard graft. She made you sit an exam before she accepted you as a student because if you weren't clever enough she didn't want to waste her time, your time and your money.
My daughter passed the Grammar school exam. None, and I mean NONE of the children in her class who went to Explore Learning did.