Some school districts had only a smattering of foreign-language speakers, so maybe that's why no one tried to teach them English.
In others, perhaps, it was difficult to find qualified staff — or these students weren't the highest priority.
But up and down the state, for at least a decade, according to the federal government, tens of thousands of English learners in elementary, middle and high school received no services to help them learn the language and keep up academically while they did, even though the law required that they get it.
Under pressure from a lawsuit and federal authorities, California pledged Friday to make sure that all 1.4 million students who are English learners receive special academic help.
The settlement with the U.S. Justice Department echoes the earlier resolution of a lawsuit covering the same ground, but goes further in establishing the state's role to ensure that these students receive high-quality instruction.
For years, California had been allowing school districts to avoid giving needed and legally required help to thousands of students with a limited ability to speak English, according to the Justice Department and civil rights advocates. The school districts even acknowledged the problem in documents routinely filed with the state.
When challenged on why California tolerated these violations, state officials insisted they had met legal oversight obligations by collecting data and by directing districts to comply with the law.
Under the settlement, state officials continue to deny that they ever did anything wrong, but they have agreed to change.
The state now commits to notifying school systems and independently operated charter schools within 60 days when it determines they are failing to serve English learners properly. It also promises to follow up in a timely fashion, with set deadlines. It isn't clear what sanctions schools would face for failing to comply, but the federal government reserves the option to take the state to court if it doesn't do its part.
"We applaud the state of California for working cooperatively with the Justice Department to ensure that all English learner students can access the language services they need to learn," Principal Deputy Asst. Atty. Gen. Vanita Gupta said in a statement.
Without saying why, the department agreed to especially close monitoring of six school systems: Burbank Unified, San Gabriel Unified and Santa Monica-Malibu Unified in Los Angeles County; Menifee Union Elementary in Riverside County; and the Santa Cruz County Office of Education and Sequoia Union High School District in the Bay Area.
About 1 in 5 California students is learning English. In a lawsuit filed in 2013, advocates determined that at least 20,000 students in 251 school districts were receiving no language-related services at all.
The suit included examples, such as that of a Compton student identified as F.S., who was allegedly denied language help in third grade, failed most of his classes and ultimately was held back. The next year, the child received help and "finally showed progress in his classes," according to the suit.
"California clearly fell down on its job here," said John Affeldt, managing attorney of Public Advocates, a nonprofit law firm and advocacy organization. "Today's settlement is an important reminder that, even in this era of renewed interest in local control, the state has the ultimate responsibility to ensure equality of educational opportunities."
The first settlement, which resolved the lawsuit, came after a court ruling against the state. That agreement established the state's role in making sure that students received at least some level of service, said Mark Rosenbaum, director of the Opportunity Under Law project at L.A.-based Public Counsel, one of the organizations that sued .
The latest settlement adds to the state's responsibility for the quality of instruction and the progress students are making, Rosenbaum said.
"A milestone settlement that, if faithfully executed, widens access to the American dream," he said.
A state spokesman called the new agreement "similar in many ways" to the previous one. But under it, the Legislature has agreed to pay for three new positions to monitor school districts, said Bill Ainsworth, communications director for the Department of Education.
Local school districts also must do their part, said Hilda Maldonado, executive director of Multilingual and Multicultural Education for Los Angeles Unified, which has more English learners than any other school system in the state.
"We have been working to tighten our own monitoring system with a new online tool that will enable us to better monitor our English learners as they make progress in overcoming their language barriers," Maldonado said.