California must find and fix its worst public schools. Here’s one way to start

California just released its third round of scores on new, tougher standardized tests, and now the state is on the hook.

A federal law requires states to identify the bottom 5% of their schools next school year and take steps to fix them. California education officials have yet to develop a detailed plan of how to do that.

Rather than wait on the state, The Times assembled its own list. We identified California's lowest-scoring schools two years ago, when the new testing regime started, and tracked their results over time.

Where they are

The bottom 5% of schools — 451 in all — are scattered all across California, from Crescent City to Calexico.

But the largest concentration is here in South L.A., where more than 50 schools ranked among the state's lowest 5% in 2015.

Where they started

As you might expect, students at these schools do not excel at standardized tests. In 2015 they saw the overwhelming majority of their test takers fail to meet standards for math and English.

On average, just 11.8% of their students met or exceeded English standards. Only 6.6% did the same in math. That was far below the rest of the state.

Where they ended up

New test scores, released Wednesday, show improvement.

By 2017, at the schools we tracked, 11% of students were meeting math standards on average. In English, improvements were greater still, with a boost to 19% meeting standards, marking nearly twice as much progress as other schools.

But here's the bad news

Not all of the schools in the 2015 bottom 5% did better. Nearly 60 saw their test scores fall even lower this year.

Here are the five schools in the group with the biggest drops in their percentage of students meeting the standards.

What to expect from the state

California has veered away from cold numbers, like the test scores we're using here.

Last year state officials began presenting scores alongside numerous other measures of success in a color-coded online dashboard. Green signals the best rating, red the worst. That tool is likely to form the basis for the state's federally required rankings.

What could go wrong

The state's complex system for ranking schools grades on a curve, which could mean that some schools where few students reach standards won't be designated as low-performing schools.

That could be the case with John W. Mack Elementary in South L.A., which is in our bottom 5% and has seen big declines in scores. The California School Dashboard classifies Mack's overall academic ranking as yellow — translation, average.

“The implication is parents might not get an honest picture of how their students are faring academically by looking at the dashboard,” said Carrie Hahnel, EdTrust—West’s deputy director of research and policy. “It communicates that things are fine where in some cases they are, and in some cases, they’re not.”

Here's who is still at the bottom

Thanks to improved test scores this year, nearly half of the schools in the bottom 5% two year ago have surpassed other schools and climbed out of the group. About 250 remain, however, and could soon find themselves under increased scrutiny.

They are listed below.