I think it was done to improve racial/socioeconomic integration, but in practice it means wealthier parents withdraw from the system and send their kids to private schools instead.
The results: 58% of SF public school students are on free/reduced-price lunches, higher than the national average. That means they're in families making $43k for a family of four (quite tough in SF).
The racial impact is also striking. San Francisco is 42% white, but in 2013-2014, only 13% of SF public school students were white. That number is 9% for high schoolers.
http://www.nytimes.com/2010/02/21/education/21sfschool.html
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Here is how the current system works: Let’s say a 5-year-old — we’ll call him Jake, like my son — wants to go to kindergarten. His parents fill out an application and list seven schools they prefer.
The more desirable schools get more applications than they have seats; in some cases that ratio is 20 to 1. That’s where the Diversity Index comes in. Known as “the lottery,” the index uses five factors to determine a child’s profile: poverty level, socio-economic status, English-language proficiency, academic achievement and, for upper grades, the quality of the student’s previous school.
Once that profile is built, the child is placed in one of his selected schools, in a class of students whose collective profile is as different from his own profile as possible. As each child is added, the class profile is adjusted, and more “most different” children are placed. Students living near their selected schools are considered first. The district also gives preference to children who have siblings at the same school and apply on time.
But there is no guarantee that a child will get in a selected school. And once the lottery has filled all the slots, those soon-to-be kindergartners who get into none of their choices are offered a place in a school with open positions. Proximity to their home and transportation are considered.
Designed to be race-neutral, the system has instead been widely criticized as too complex and opaque. “It’s all magic and voodoo,” Ms. Menegaz said, only half joking.
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Basically, they try to balance out the schools, but it means that if you are of a higher socio-economic status you are placed into schools with people with lower socio-economic status to try to balance things out. But that often means being placed into schools that are farther away, and don't perform well. So, it pushes away people from public schools who can afford to move away, or send their kids to private schools (this is why we left San Francisco).
Is there _any_ system that can "guarantee" that a child will get in a selected school when there are big demand-supply gaps?
I think you're looking for a market? There never seems to be a problem getting e.g. a haircut, in any community.
Better hairdressers are paid more money. If the same were true for teachers, they would "scale" too.
That's not accurate, a major part of Jerry Brown's education policy changes have been improved funding for title 1 schools (low income criteria - which most or all SF public schools meet) at the expense of non-title 1 schools. The measure is the Local Control Funding Formula.
You are directionally accurate in that CA law greatly reduces the ways cities can put money into the operating budgets of their school districts. However, there are plenty of ways around this, if people were strongly invested in building better schools in SF they would be using them.