Instead, we're still forcing students into rigid cohorts based mainly on age, effectively optimizing for the statistical mean while leaving both ends of the ability distribution poorly served. This is particularly wasteful with gifted students who could be advancing much faster if the system accommodated their pace of learning.
The tech to deliver adaptive education at scale exists today. The main barriers are institutional inertia and perhaps a misguided egalitarian impulse that confuses equality of opportunity with enforced uniformity of outcomes. We should embrace the natural variation in human capabilities and build systems that help each student reach their potential, rather than constraining everyone to march in lockstep.