As a kid, I never saw it's relevance in my everyday life and I still don't. Other than simple mental arithmetic, decimals, percentages and fractions, I haven't used anything that I learned in GCSE maths in my everyday life since I got my GCSE (7 years ago). In fact I've barely even used any of the things I just mentioned (mostly just basic mental arithmetic).
I knew when I was in school that I would never do A-level maths or a maths related degree/career so I resented being forced to learn anything other than elements of mathematics that I would actually need to function in society. Don't get me wrong - I realise how important maths is because without it we wouldn't have people who could build/design houses/cars and we wouldn't have amazing doctors and physicists and all sorts of other things. However - those are the kind of people who study/studied maths because they wanted that career or just enjoyed studying maths. I never wanted a career which was dependent on my mathematical ability and I was much more interested in the arts than the sciences (though I can see the value of the sciences very much!). Also, I recognise the importance of maths if you are working on a till in a shop etc, however you do not need to understand or even know about vectors and trigonometry etc. in order to function in your everyday life. It is totally unnecessary.
I consider my GCSE Maths grade to be completely unrepresentative of my actual mathematical ability - I got a good grade but it was long time ago and I basically forgot it all within a week of sitting the exam. I can do basic maths - I've forgotten everything else and in the 7 years that I've been living in the 'real world', I've never needed to dig out my old GCSE book in order to remind myself about cumulative frequency or whatever because I've never been in a situation where I've gone ''damn, I can't do my job/use the kettle/get on the bus, without knowing how to plot a scatter diagram''.
Conversely, I always saw the usefulness of English in school and I didn't feel frustrated by being forced to take English GCSE because I knew that when I left school I would need to know how to use the English language correctly in order to apply to jobs/write a CV and to do paperwork in my job (and yes there are bits of maths but it's basic - primary school difficulty at best!).
I honestly believe that schools at the moment (and when I was there) are useless for setting young people up for the real world - teach them what they need and then offer them the option of learning other things. No one ever taught us about pensions, looking for work, managing our money, career progression, family issues, drugs/alcohol, medical access etc. If anything like that was covered it was in those crappy weekly lessons with a form tutor which in reality consisted of a class of 30 odd kids doing crosswords/wordsearches with the words 'jobcentre', 'condoms', 'responsibility' etc hidden in them and then 50 minutes of free time.
So basically, I can only speak for myself - but when I was at school I thought (and got the distinct impression that my friends thought the same) that anything that wasn't actually going to be of use to me was a complete waste of my time. I still feel that way. I can read about all sorts of stuff in my spare time - and I do enjoy doing so. I don't need to be force fed knowledge by the state other than knowledge that will help in a practical way.