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<p>When I went to high school, the standard sequence was:</p>
<p>Algebra I
Geometry
Algebra II
Precalculus
Calculus (only one class, teaching to the AP BC syllabus)</p>
<p>Obviously, you needed to be in at least Geometry by 9th grade to reach Calculus by senior year. This was less than 10% of the students then, but more now. Back then, maybe one student every few years was two years ahead, in Algebra II in 9th grade. Most of the students who reached Calculus took the honors versions of Geometry, Algebra II, and Precalculus.</p>
<p>Today, the same high school has essentially the same math course sequence, but there are more one year ahead students and probably a non-trivial number of two year ahead students (who will reach Calculus by junior year). They also have an AB option as well as the original BC course – a student who completes Precalculus by junior year takes either AB or BC (not AB one year and BC the next year).</p>
<p>A course covering the AB syllabus approximates a one semester college or university calculus course. If that course is over a whole year, it would be at a slower pace than a college or university calculus course. A course covering the BC syllabus approximates a one year[li] college or university calculus course.</p>[/li]
<p>[*] Colleges and universities do vary; at some, there are topics in freshman calculus not covered in BC. Some super-elite science and engineering schools make everyone retake freshman calculus because their courses have a lot of extra theory.</p>