Jack O'Connell is state superintendent of public instruction.

When I was a high school teacher, I always looked forward to watching my students receive their diplomas on graduation day. Now, as state superintendent of public instruction, I am working to close the achievement gap that prevents many students from celebrating this proud day.

Recently released RAND research shows that the achievement gap begins at the starting gate, when kids who have not attended preschool first enter their kindergarten classrooms without knowing their letters, sounds, shapes, colors or numbers.

Children who have not gone to preschool often lack basic social skills, as well, such as playing cooperatively with others or caring for themselves and their belongings.

This school readiness gap mirrors the achievement gap in later grades. Students who start school behind tend to stay behind, and this happens for too many children.

While large percentages of all children fall short of state standards, some groups of students are falling short by even larger margins. They include English learners, students whose parents did not graduate from high school, African Americans, Latinos and economically disadvantaged children. For example, 72 percent of African American third-graders and 77 percent of Latino third-graders did not meet state standards in English-language arts.

The RAND research confirms there are persistent achievement gaps in our education system that California simply cannot afford to accept – morally, economically or socially.

It adds to a mountain of data showing that effective preschool raises achievement levels for all children, and it offers real hope for closing the school readiness gap.

Research shows that children who attended quality preschool scored higher on eighth-grade reading and math tests. They are less likely to be placed in special education and more likely to graduate from high school. They were more likely to hold jobs and earn more than kids who didn't attend preschool, and less likely to receive public assistance or be arrested. The evidence is clear: Preschool has powerful positive benefits for children's life chances and ultimate well-being.

But not all preschool programs yield these positive returns. Effective preschool starts with expert, well-trained teachers. It is both purposeful and playful, and helps instill in our children a joy for learning as well as sharing and getting along with others in a richly stimulating environment.

High-quality preschool gets kids ready to learn. The California Department of Education, in consultation with early childhood educators, is developing preschool "learning foundations" – guidelines that will help children develop the social, emotional, physical development and prereading and premath skills they will need when they enter kindergarten.

Student achievement starts with effective preschool, but it doesn't end there. Three years ago, I established a statewide P-16 Council to examine ways to improve student achievement at all levels. I've charged this group – composed of leading educators, respected employers and committed community leaders – to spend this year gathering research and studying strategies for closing the racial and economic achievement gaps that threaten our state's future.

We'll be examining these strategies, including access to quality preschool, at an Achievement Gap Summit I am hosting in Sacramento next week. Thousands of educators will focus on ways we can help all students achieve their full potential and prepare them to compete in the competitive global economy.

A number of speakers and workshops will focus on preschool's role in closing the readiness gap before it becomes the achievement gap. Those sessions will feature experts highlighting findings from the RAND California Preschool Study and exploring how California fits into a growing national movement for effective preschool. The P-16 working groups will also convene to discuss emerging policy recommendations on education reform, including preschool.

The achievement gap threatens the future of thousands of California students and the economy of our state. I am convinced it is possible to close that gap but not unless we start before kindergarten to level the playing field for children who start school behind their peers and behind their potential.