<p>Just a couple of thoughts on the main topic and the “sub-discussion”</p>
<p>I don’t think it is possible to teach a good high-school course in chemistry or physics to students who do not understand algebra. Trigonometry has been listed as one of the more useless topics, but trigonometry is needed for a reasonably good high school physics course, as are vectors (obviously).</p>
<p>In my opinion, one of the advantages of mathematics courses (and good chemistry and physics courses) is that they illustrate to students that there are elements of reality that are beyond the reach of authority, charismatic persuasion, or slick debate. Ideally, the student understands enough to obtain answers for him/herself–to simple questions, true–and to know to stick with them, even when others may be arguing against them. Also, the courses offer one of the few instances in the high school curriculum where a student can encounter an idea that he/she just doesn’t get, pour effort into the subject, and then get it. This is one of the most desirable experiences for a student to have, in my opinion. </p>
<p>If a person thinks that algebra is about “learning algorithms,” then I suspect that the person does not understand algebra.</p>
<p>On the sub-topic: It is quite difficult to figure out what math a student is ready for, especially with the non-mathematical outcomes (e.g., admission to a top college) rather closely tied to mathematical placement.</p>
<p>I think it is possible that in the future, public schools may be able to offer individualized instruction in mathematics via the internet, which might allow for as many paces as there are students. This would be my preferred solution.</p>
<p>In the meantime, the idea that students may hit conceptual “walls” is very real, I think. Some schools deal with this by eliminating troublesome topics from the curriculum. For example, many high schools now teach geometry without proofs (though that seems like an oxymoron to me). Schools that include proofs in the geometry course may omit solid geometry or–even more likely–locus. As ucbalumnus notes, a number of schools spread the Calc AB/BC curriculum across two years. This makes no sense to me if the two-year version is compulsory for all. The delta-epsilon concept of a limit has been removed from the AP Calculus curriculum, even in the BC course, though it may be taught to fortunate students in some schools. My university has actually removed the delta-epsilon definition of limit from the first-year calculus courses. In a way, this makes a (twisted) kind of sense: The students who are taking introductory calculus at the university either did not have it in high school, or didn’t get it then. Students often struggle with the delta-epsilon ideas. Removing it leads to fewer student complaints. The students who took AP Calculus didn’t see it either (for the most part), so no one really knows that it is missing . . . until they hit real analysis, of course. I don’t think a student has taken real calculus unless they have worked with the delta-epsilon concept of limits. Actually, I’d like to see that students understand uniform continuity, and see proofs of methods such as the chain rule, for a real calculus course.</p>
<p>I’d like to see schools offer what I’d call “way station” mathematics courses, for students who will continue in math, but who genuinely aren’t ready for the leap of conceptual complexity that the next course requires. How to identify the students who really should spend a year on mathematical “pause,” how to make it acceptable to the striver-class to take the course, and how to keep it from being the slacker-default would all be challenges, to be sure. At the university level, the mathematical curriculum usually has so many offerings once a student gets beyond the introductory calculus/diff eq sequence that it is possible to tune the course selection to the stage of mathematical maturity better than in high school.</p>