From reading your comments, is it true it's mostly boys who love maths?
Have your sons always loved maths?
My ds2 is only in year 3, but he has loved maths since he could count. He is a wild, boisterous boy, and to get him to sit still I just ask him to do his 34 times table (or any number). Of course he can't, but he's happy to sit there adding on in 34's and writing it. He loves making things, has helped measure, make bird boxes, curtains, cupboards, cakes, all sorts of things. He loves numbers. His problem in year 3 is showing his working out because he "just knows" some things. And he knows them very quickly.
But he doesn't read despite many attempts to encourage him. I have no idea about the 11+ and haven't looked round the boys grammar, but already I can see him loving dt, textiles, art, product design, food tech - and maths! Not English or languages. He wants to be a builder. I'm all for it. He can build us a house - and he'll always have work.