>>534358495
It's a smaller school, established to be much younger than the rest and with a very specific focus and reputation
As far as we know, there is no millennium elementary & middle school to supply the high school. No one is going there just because it's part of the sequence and transfering elsewhere would be too much effort
Anyone going there has CHOSEN to do so, and thus is far and away more likely to have an interest in something that they want to pursue, and thus won't become random troublemakers who dropped out because they couldn't handle 9th grade algebra

My headcanon is that they're partially responsible for most of the other schools being filled with retards, brain drain and all that