The vast majority of students in Alameda will complete high school and not drop out, bucking a statewide trend, according to what state education officials say is the most accurate-ever analysis of dropout data.

The dropout rate at Alameda High School was just 1 percent during the 2006-07 school year, while at Encinal High School it was 2.1 percent.

The numbers were not so positive at Island High School, the continuation campus which serves about 186 students. Just over a quarter of its students dropped out during the year, data from the state Department of Education released Wednesday shows.

"Once a student starts falling behind, it can be very difficult to turn things around," said Mike Cooper, Encinal High School principal and a former administrator at Island. "But we do try to do everything we can so that they can recover their credits and graduate."

The data — based for the first time on actual student tracking rather than an estimated formula — shows that 2.9 percent of high school students in Alameda dropped out in the 2006-07 school year. The four-year average dropout rate for the district is 11.2 percent.

The four-year dropout rate statewide is 24 percent, a figure that has alarmed state education leaders.

"Twenty-four percent of students dropping out is not good news," state education chief Jack O'Connell said at a Wednesday news conference. "In fact, any student dropping out of school is one too many.

In the past it has been difficult to determine how many of the state's students drop out of school. Last year the state assigned students identification numbers to help track their whereabouts in the educational system. The result is more accurate data, which also indicates higher dropout rates than previously thought.

"For too long, we had to rely on complicated formulas to make educated guesses about how many students were graduating and how many were leaving school without a diploma," O'Connell said. "Using student-level data, we can improve the accuracy of our count of how many students drop out, increase accountability and focus on preventing dropouts."

The state dropout average is higher than in Contra Costa County, where an average of 21.5 percent of students will not finish school, and Alameda County, where the drop out rate hovers around 19 percent. Solano County's 4-year estimated drop-out rate is more than 30 percent.

Some East Bay school districts' dropout rates soared much higher than that state average, however. About 40 percent of Vallejo and West Contra Costa County district students drop out of high school, while more than 37 percent of Oakland students drop out, according to four-year averages calculated by the state.

Two years ago, California assigned every public school student a unique state ID number in order to track their progress, regardless of where in the state they moved. If a student vanishes from Alameda High School, for example, and turns up in Los Angeles Unified a month later, that student will no longer be considered a dropout. The system does not track students who move out of the state or country.

Unlike previous reports, which account only for graduates and dropouts, the new system includes other categories, such as students who are still preparing for the high school exit exam, for example, or who are enrolled in an adult school.

Dozens of states already use the same method, which was encouraged in a graduation compact signed by all 50 governors in 2005. It is widely considered the only way to accurately gauge what happens to high school students, particularly in areas with high levels of mobility.

The governors' compact followed a high-profile study by the Harvard Civil Rights Project that concluded that California was reporting an unrealistically high graduation rate.

"The implementation of the student identification system will provide more accurate data, especially in the area of high school dropout rates," Alameda school district Trustee Mike McMahon said. "Given it is the first year of real data, we need monitor it."

Cooper said he expects teachers and administrators will be reviewing the numbers when students return to class this fall.

"It's always in the forefront of our minds," Cooper said about the dropout rates. "We are always thinking about how can we can keep kids engaged and moving forward."

Staff writers Katy Murphy and Kimberly S. Wetzel contributed to this report.