I just did that test, and I couldn't answer more than half of the questions. My maths teaching was appalling, and I am of the slightly younger scale of MNers.
I think part of the problem is that maths is difficult for some people. And it's boring to people who find it difficult. There is only so much you can jazz up maths. At some point, you have to settle down and start fucking around with quadratic equations.
So, maths classes can be difficult to engage once you're out of the higher sets. but because the curriculum is so target driven, it doesn't allow for the fact that 70% of school leavers will never ever need to use any of the maths they have learned by age 11.
We need two maths classes. It should be mandatory, no argument with that, but we need basic and higher sets, and none of this bullshit about putting all the dim kids in basic and most in higher. You should only be going in the higher set if you need it for further education, such as Physics, Maths, IT or Engineering etc.
EVERYONE else (wannabee social workers, nurses, shop workers, office workers, managers, police officers etc) should be doing basic maths, where their fucking precious life is not wasted on quadratic equations they have no interest in, will never understand, and will forget about the second their maths teacher is not staring directly at them. When was the last time you NEEDED to do a quadratic equation?
They need to be concentrating on making sure the basic maths NEEDS have settled into their brain, such as percentages, multiplying and dividing high numbers, understanding pie charts and generally backing up everything about maths that they should have learned by the time they are 14, and not trying to cram in useless (to the majority of the population) information that they won't understand, have zero interest in, and will never ever want or need.