The public "school" sends a bus to pick up and drop off junior. The "school" makes little effort to actually educate junior but its function is really to be a very expensive babysitting agency. Kids are interested in sex at 12 years old? The school will provide condoms which will keep the kids out of people's faces and out of their hair after school. The school will provide courses in "how to do it" in as any different ways and with as many different kinds of "partners" as the mind can imagine. to the young teen student, what is more interesting: Sex or algebra, physics, history, Shakespeare?
The "public school" provides lunch (and increasingly) breakfast) to the kiddies. This lets welfare mommy sleep in until noon and not worry about using HER food stamps to feed the kiddies.
The school provides entertainment: football, baseball, basketball, marching band, hockey, proms, art, music, etc.
Missy is pregnant and just cannot let her parents know? No problem. The school nurse will arrange her abortion and mom and dad will NEVER know! Who imagined that adults could be sooooo cool!
OK, so the kids graduating are often functionally illiterate and innumerate. When they start the four year party that is college, they can get credit for Remedial English, Remedial Math and Remedial Alphabet.
And getting heavily taxed to support a massive welfare state and the 47% who pay no taxes at all. Some of those 47% even get "refundable tax credits" in addition to the regular straight-up transfer of wealth programs.