The family live on the boundary of the two London boroughs and wanted Declan to go to the local school. "I wouldn't be interested in sending him to a school if it was ranked slightly higher but was miles away," said Mr Brennan.
"We sent Declan to Grey Court because it is local. It was the only school he could have gone to. The only other is two bus rides away.
"Grey Court has been put under special measures but it's a good school, I think," said the 44-year-old. "It's in lovely grounds and has lots of fields so there's no reason why it shouldn't be a good school. It's just over a mile away, so we are lucky in that respect."
He does not believe Tony Blair has made education his top priority and said: "He's always been a good man for a soundbite. He sends his children halfway across London so they can go to a good school."
Mr Brennan thinks schools should select by catchment area - where people live. "It would be nice if parents had real choice but I don't think they do," he said. "The issue is not about choice, people just want a good local school."
Milton Sills, a timber industry procurement manager, was unable to get his daughter in the family's first-choice school and is now paying for her to be educated privately.
Bethany, 11, is a pupil at Surbiton high in south-west London, which charges pound;9,150 a year.
Mr Mills, 46, said: "We tried to get her into Tiffin girls', a selective state school in Kingston, but she didn't get a high enough mark in the exam.
"She went into a mixed state school where she was one of only six girls in her class and was not happy there. Whenever she went into the playground people were swearing. Because there were so few girls you can imagine how much attention they get in the playground.
"Even though we can't afford it we weren't prepared for her to spend the next five years in that school. She spent two days there and we went to the bank and borrowed the money we needed to pay for Surbiton high."