Working in schools (an occupational hazard of being a teacher) I have come across Brain Gym on a number of occasions. In case you don't know, Brain Gym is a system of kinesthetics that puts forward the idea that certain exercises and postures aid children's learning. It is widely used in British state schools.
However, despite its popularity, like anything that's successful, it comes with its very own controversial baggage. There are those who have disputed the validity of Brain Gym's theoretical foundation and its alleged results, citing it as an example of 'bad science'*.
You can find out more about the proposed benefits of Brain Gym as an aid to children's learning here, whereas you can read more about one sceptic's view here.
Personally, I don't feel well-informed (or practised enough in this area) to make a call one way or another. All that I would say is that even if the science behind Brain Gym wouldn't stand up to in-depth scientific scrutiny, if the simple action of carrying out the Brain Gym exercises before starting a lesson or a task helps a child focus on the work they have to do then is that really such a bad thing. After all, placebos have been proved to make a difference in certain medical trials.
Maybe it's just a case of mind over matter, but if that is the case, then it doesn't matter and I don't mind. If it works for you...
* What's 'good science' then? The atom bomb?