Bribing children to do well at school isn't going to do anyone any favours, it only sets them up to expect to be rewarded for doing the most basic of things in later life. There are plenty of kids who go to school and work hard because they simply just want to do well, they know that grades are important and whilst good marks aren't the most important things in life, they certainly do make a lot of things easier in the long run. If you work hard, you get rewarded by achieving good grades, which leads to a university place, which leads to a decent job etc.
EMA was brilliant for the kids in the lower income bracket, though. I'm sure some abused the system, like every system gets abused, but it would have made a huge difference to the large majority.