Our school system went through a period where they tried to get 90% of kids through Alg I in middle school – in part because the STEM magnet was doing it so effectively. It didn’t work out well, and the pendulum has swung the other way – now getting into the Alg sequence early is almost impossible.
I spent most of S2’s freshman year of HS having him work in Jacob’s Algebra I while he was taking Alg II, because the Alg “lite” was so unsatisfactory. His Alg II teacher attended MIT and knew what they should have covered.
S1 and S2 were only two grades apart, but the difference in pedagogy during that time was HUGE.