The problem with education is that it always has a different take on a subject to what personally fascinates you about the subject. Subjects that might have floated your boat personally for many years will be taught differently to what you expect, killing your interest in a subject.
There is an adage about teaching - if you cannot do then teach, if you cannot teach then teach Geography. If we take Geography as an example, you might think of geography as being about places on a map, be able to name all U.S. state capitals and know where Dhaka is and Dakar isn't. Then, in a geography class, you might find that knowing where anywhere is does not matter in the least. 'How flood plains are formed', 'how a volcano works' will be what is taught, without any mention at all of physical places.
The geography example is an example of how expectations of a subject can be wrong at the basic school level, you can live with a mis-match of expectations in geography syllabus, however, go to university and it is another kettle of fish. You might think politics would be a useful thing to study, be passionate about the subject and be knowledgeable about current affairs. Again, none of that would matter.
Computer science is another area of concern. You might be good at programming and be up to date with whatever is on HN. Yet, at university you might get taught languages and methodologies that are a world away. There might actually be reasons why the university teach what they teach that are not readily apparent. The military might have some link up that means that stuff that matters to designing jet fighters gets taught. Clearly none of it - 'ADA' - for instance - might have no relevance in the real world.
Returning to your subject of maths, in the real world you are doing pretty well if you have problems that require secondary school stuff - trigonometry, calculating prices with tax, differential equations. Actually you could probably go a long way on getting a man on the moon with secondary school maths, yet there is a whole world of maths beyond that. Triple integrations, anyone? Even if you do find a real world use - electronics with Gauss's theorem - there aren't many uses for that real world use. It is all too convenient for maths to be taught in such a way that it is abstract and not practical, e.g. teaching a program to do it for you, or working on a large dataset in a computationally efficient way. Even reading the data in is not something that would be taught. It is a bit like how you can do a degree in electronics and never touch a soldering iron or know how to fix a fuse.
So my suggestion is to not head off to university so hastily. Work somewhere for a little while then go to university because you know why you are going. You can actually learn useful stuff at university rather than go there to just get a bit of paper.