OAKLAND -- Redwood Day School is expanding its middle school, opening up new opportunities for the increasing number of students in the East Bay applying to private schools.

The school will increase its middle school population, which is grades six through eight, over three years, beginning in the fall of 2013.

"It allows us to decrease our class size, which is huge," said Head of School John Loeser.

Each year, the school will add one extra sixth-grade class, which will increase the number of open slots for new students and reduce the number of students in each class from 23 to 19. Previously, only three or four slots for new students would be available in sixth grade. The added classes will also help students who have been together for a long time to forge new friendships.

Loeser said that although the board of trustees of the school, a nonprofit, only approved the expansion recently, applications for middle school have already increased about 75 percent as news of the expansion leaked out.

"I think there was this buzz of excitement," he said.

Redwood Day School, which is also celebrating its 50th anniversary, has about 350 students, which will go up to 385 over the period of the expansion. It is located just off the MacArthur Freeway near Fruitvale Avenue on grounds the school owns. For now, there is room on the campus for extra classes, but eventually the school will expand its facilities to make room for the larger middle school and other improvements. Funds for the current extra classes are built into the budget for now, Loeser said, but the school will have to raise funds when it expands the site.

The school is also kicking off its new strategic plan this year, which emphasizes science and technology as well as language instruction on top of the school's existing focus on academics and social growth.

"We are trying to create well-rounded students," Loeser said.