More California students are taking eighth-grade algebra than in previous years, but many of them are also unprepared for it and failing.

Those are the key findings of a new study released Friday by EdSource, a Mountain View-based nonprofit focused on educational research and issues.

Statewide test data indicated that schools increased the number of students taking Algebra I in eighth grade by 80 percent between 2003 and 2010. The increase has come with the state’s push to improve students’ algebra skills.

However, the study found that math preparation varied widely among students and that many eighth-graders were not prepared to succeed when placed in Algebra I.

Educators in San Mateo and Santa Clara counties said they do everything they can to make sure students are prepared for algebra.

“We take math placement in algebra very seriously,” said Lynette Hovland, director of curriculum and instruction for the San Carlos School District.

To determine whether a student is to be placed in that course, she said, the district looks at several factors, including the child’s grades, class participation and performance on an algebra-readiness test.

San Jose Unified uses similar measures, spokeswoman Karen Fuqua said. The district also provides algebra students a math lab that reinforces the concepts they are learning.

“It’s how we support students along the way (and) not waiting until they are completely off track,” Fuqua said.

San Mateo and Santa Clara counties mirrored the state in the increased percentage of students taking algebra from 2003 to 2010, according to data from the California Department of Education.

Like in other subjects, Peninsula and South Bay students fared better in algebra than their peers statewide.

Both San Mateo and Santa Clara counties saw 55 percent of eighth-graders scoring proficient or advanced in the state standardized test for Algebra I in 2010 — up from the 50 percent in 2003, according to the state Education Department.

In contrast, 46 percent of eighth-graders statewide reached at least the proficient level last year — up from the 39 percent in 2003.

The EdSource study, “Improving Middle Grades Mathematics Performance,” examined test scores of almost 70,000 eighth-graders statewide. About a quarter of these students scored low on the state test for seventh-grade math, the study said, but of these children, 30 percent were put in Algebra I despite being unprepared.

The majority of those students scored below the basic level when they took the state test for Algebra I, the study said.

The state’s focus on algebra in recent years has benefited low-income, African-American and Latino students — many of whom previously did not have access to the course in middle school, the study said.

But that focus also may be partly motivating schools to make premature placements, said Matt Rosin, EdSource senior research associate and one of the study’s authors.

In addition, the study found that only 34 percent of school districts had explicit placement criteria, Rosin said Friday. The majority of districts did not have such criteria and left placement decisions up to individual schools.

Among the study’s other findings is that schools serving mostly low-income students placed higher percentages of children in Algebra I than those serving largely middle-income youths.

The study’s authors urged districts to prepare children for algebra early on and improve eighth-grade math placements by taking into account wide variations in student readiness.

“California’s middle-grades educators should continue to widen appropriate access to challenging mathematics coursework,” Rosin said in a statement. “But in doing so, they need to build on a strong math foundation for students in earlier grades and base their placement decisions on a careful understanding of students’ preparedness.”

Rosin added: “The objective of giving more students the opportunity to complete Algebra I in eighth grade should not be achieved at the expense of a large proportion of students who would be better served by having more time to master key algebra concepts.”

To see the full study, visit www.edsource.org.

Contact Neil Gonzales at 650-348-4338.