[dragonwriter]

> Charter schools do this by various selection effects, and artificial barriers, like ending at noon on a Wednesday. So the only kids who go there have two parents, one who probably is stay at home and can pick the kid up

This would be a more effective filtering technique if inconvenient minimum days weren't common in regular public schools.

The most effective filtering technique used by charter schools is... being a charter school.

Because it isn't the default option public school based on residency and requires an active choice, it automatically filters for active parents.

And because for most of the potential student base its farther from their default public school, it selects for logistical flexibility (loosely correlating to wealth and/or having a parent at home) as well.