It's actually not. It's not clear from the way the article is written, but he's talking about two different things, both of which various reform bodies have proposed eliminating. The first is "gifted and talented education" programs, which involve additional coursework and activities on top of normal schooling. I'm not going to claim I remember super well what we did at this point, but I do remember learning how to make donuts from scratch, holding mock trials, learning computer-aided design at a time the regular school system didn't even have computers yet, and taking the SAT in 6th grade. All of these happened either after school or in the summer.
The other thing is related to tracking. That is where Algebra comes in. Not all students will take it at the same time. Instead, students are segregated into separate tracks, one of which will start with Algebra in middle school and eventually end up taking Calculus by the end of high school. The other won't get to Algebra until high school and will never take Calculus at all.
These are separate phenomena, but the author here is drawing an analogy between the reasons given for eliminating both GATE programs and educational tracking systems (as in, both are seen as being racially biased).