Tens of thousands of California students are passing two key English tests but haven't been declared fluent in school, according to a Register review of state records.

Students could still be labeled "English learners" because of low academic achievement, rules for becoming fluent that vary by district, and, possibly, money, researchers say. Schools statewide could have lost an estimated $53.7 million if students who scored well on the state tests were declared fluent, according to state records.

And a state incentive program that offers cash to schools for declaring students fluent has never issued a reward because it lacks funding, state education officials said.

Although test scores have been rising for English learners, only 8 percent of students were designated fluent last year. As many as 15 percent of the state's English learners scored high on two English tests over the past year and a half.

"I worry that some districts keep kids in English-learner status longer than really needs to be because they get money for those kids," said Paul Warren, an education analyst in the nonpartisan Legislative Analyst's Office.

But state education officials point out that schools also have incentives to label students properly, such as eliminating the time-consuming tests that are given each year to English learners and complying with a new state accountability system that starts this year.

Determining who is actually fluent helps ensure that students are placed in the right classes and challenged enough by teachers, researchers say.

A student can be labeled an English learner for a variety of reasons. According to the state, English learners speak another language at home and have low skills, entitling them by law to extra help in school. Some, especially those in the early grades, are learning to speak English, but most are learning academic skills, such as how to write an essay or pass a standardized test. About 84 percent of the state's English learners are Latino.

State test scores suggest more of the state's English learners could be fluent than districts have reported. For instance, last school year, 402,916 students in grades 3-12 passed the California English Language Development Test, or CELDT, which tests English learners in listening, speaking, reading and writing.

A few months earlier, in the previous school year, 363,447 English learners passed the California Standards Test in English, which is given to all students in grades 2-11 every year.

Only 120,122 students were declared fluent last year by schools, however.

That means as many as 243,325 students statewide, about 15 percent of the nearly 1.6 million English learners, scored high on the two exams, but weren't declared fluent. It is a rough estimate because state records don't show if the students who scored high on both exams are the same.

Others have raised concerns about the fluency rate. A year ago the Legislative Analyst's Office urged the state Legislature to investigate gaps between the number of students who scored high on the CELDT and the number declared fluent.

State officials caution that the CELDT is just one of four criteria required to measure fluency. Other measures include the California Standards Test, students' grades and the parent's input. The state allows each district to add its own criteria.

But the analyst's office said large gaps could point to other problems.

A Register analysis of the 4,600 schools that serve most of the state's English learners found gaps in most schools.

More than 1,100 schools statewide had at least 100 students, and often many more, who scored high on the CELDT but weren't declared fluent.

Santa Ana High had the highest gap in the state - 950 students. Overall, the school reclassified about 10 percent of its students as fluent last year.

Los Amigos High in Garden Grove Unified followed closely with 651 students. Less than 1 percent of the students were declared fluent last year.

At Santa Ana High, officials said they are looking into the reasons for the gap, but it could be academic skills, which they work on daily. Students write in all classes, including science and dance, and are tutored if they fail. Test scores are rising as a result, officials say.

"Our standards are higher and our kids are handling it," Principal Dan Salcedo said.

The rate at which schools declare English learners fluent varies widely in Orange County, from 3.1 percent in Huntington Beach's high school district to 40 percent in Laguna Beach.

Garden Grove Unified officials, for instance, say they have high standards for fluency because they want students to succeed. The district added its own writing test to the state's criteria, but some districts didn't.

Jay Heck, who supervises Garden Grove Unified's Assessment and Registration Center, said he would "welcome ... consistent criteria from district to district."

State funding, a critical source for all districts, could also be an issue. Last year the Legislative Analyst's Office urged the state to change the way the money is distributed for English learners because schools receive special funding for those students.

The largest program is Economic Impact Aid, which gives nearly $500 million a year to school districts with English learners and poor students.

If the students who passed the state's two English tests last year had been declared fluent, the schools would have lost $53.7 million from this pool alone, an estimate based on the most recent budget.

Schools receive other funding for English learners, such as $53 million this year for the English Language Acquisition Program to help students learn English. The program includes the state's only incentive, $100 a student, to declare students fluent. But the state has never provided enough money to fund the award, state education officials said.

School officials say money is no incentive to keep students off the fluent list. Students remain on English-learner status because they need the extra help the money provides, they say.

"They can keep their money," Santa Ana Unified Superintendent Al Mijares said. "My biggest interest is that our students learn to read, write and speak English in its highest form."