There's a famous post by Erik Hoel that calls the human version of this Aristocratic Tutoring [1] (Scott Alexander is unconvinced [2]).
In the 1980s, a researcher called Benjamin Bloom claimed a z=2.0 (that is 2σ) advantage for a combination of mastery learning (don't move on the the next topic until you've mastered the current one) and 1-on-1 tutoring. Later replications show there is definitely something going on, but the effect size is much lower, for example around z=0.7 in a 2020 paper [3].
I'm still open on AI tutoring, though the Dartmouth results look impressive. Someone please try and replicate this.
There's a saying that AI helps the best students get better, and the worst ones get worse. (Anthropic sort-of agrees [4].) It'll be interesting to see how that turns out.