http://www.bbc.co.uk/news/education-18522634

Around 25 years ago I understood the special place of mathematics in kids education and then got our lads into it . A simple proposition : the more maths  you study the higher income you end up with . This is true now as it was then. A ton of US studies show that and class is not a factor at all .

 As I have said to many youngies over the years:  " Its not the maths itself that makes you more intelligent but the way maths is studied which in my view is more like music or even skateboarding practice, the big exception being the problems are more complex and get you thinking very clearly ". The intelligence boost comes through working over the complexity repeatedly until the problem is solved.