I'm currently a second year engineering student. In first year, we had several mature students (aged late 20's to late 60's) myself included. The people that survived were the ones who took advanced math courses in high school, or retained their prior knowledge of math. Those who did not have a strong math background dropped out fairly quickly, even though the first term math was considered a 'remedial' math course (covering basic algebra and trig, stuff I did in grade 10). Those with poor math backgrounds quickly floundered and failed out (a couple of the more tenacious types stuck on, but they had to re-take the course and are now severely behind).
But really, if we're only going to teach the basics to everyone and leave specialty courses to when you've chosen your field, then why not eliminate the need for English after grade 10 for those not pursuing a degree in it? get rid of all science classes for MBA and Economics students too; no more history classes unless you plan on being a history major or social science classes unless you're gonna be a sociologist.
The point of high school is to provide a well-rounded, general education is just about every academic discipline. To do this, a certain level of math proficiency is required. While I agree that calculus isn't necessary for most students, normal math classes all through will be. Even if you will never again have to sketch a parabola, or solve two unknowns in two equations, having a knowledge of math that is significantly higher than required will not only make the maths that you need to know for life much easier, it will also enable you to expand your horizons later in life if you choose to.