Good teachers make all the difference. According to research by academic-testing expert William Sanders and others, the effectiveness of the individual classroom teacher is the single biggest factor affecting students’ academic growth.

In one study, for example, Sanders found that students who had been taught by three ineffective teachers in a row scored below the 50th percentile in mathematics by the end of the third year. By contrast, those with three highly effective teachers scored above the 80th percentile. Teachers’ effect on academic growth dwarfed other factors, such as class size, that have been given so much attention.

In California, too few students have access to qualified teachers, especially in schools serving children of color and children from low-income families. The Center for the Future of Teaching and Learning reports that in schools with the highest percentages of minority children, more than 20 percent of teachers are underqualified, compared with 5 percent of teachers in schools serving a low percentage of minorities. Perhaps not coincidentally, in the lowest-performing schools, as ranked by the Academic Performance Index, 1 in 5 teachers is not fully credentialed, compared to 1 in 20 in the highest- ranking schools.

Stanford University economist Eric Hanushek found that having good teachers five years in a row could eliminate the average achievement gap between poor students and their higher-income peers. Clearly, if we want to give all children a chance to succeed, we need to invest in the quality of our teachers. We need to give teachers good preparation before they enter the classroom as well as continued support and opportunities to develop their skills after they begin teaching.

Comedian Bill Cosby knows the importance of teachers, and, in fact, attributes his own phenomenal success to a teacher. As a sixth-grade student in Philadelphia, he was inspired by his teacher, Mary Forchic, to follow his dreams of becoming an entertainer. Recognizing his natural storytelling abilities she suggested to him that he “become either a lawyer or an actor, because you lie so well.” Forchic remained one of Cosby’s lifelong friends.

Cosby has devoted a great deal of his time to ensuring that all children have the opportunity to benefit from teachers like Forchic. An example of his efforts to promote effective teachers for all children will be seen today. Partnering with Stanford’s School of Education, Cosby is “celebrating teachers” in a benefit performance on the Stanford campus, with proceeds going to teacher fellowships. Cosby’s performance will be followed by a fund-raising dinner hosted by another teacher advocate, TV journalist Tom Brokaw, and preceded by a conference honoring a group of extraordinary Bay Area educators. The goals of the events are to call attention to the importance of investing in teachers and to honor teachers for their commitment and hard work.

We could all follow Cosby’s lead and express our gratitude for the enormous contributions that dedicated teachers make to our children’s lives and to our community. So many teachers in the Bay Area are at school early and stay late, correct papers and plan instruction evenings and weekends — working hard to meet the educational needs of students, some of whom struggle to make progress despite the stress of living in poverty, lack of proficiency in English and many other challenges. Teachers buy materials with money from their own pockets and volunteer their Saturdays and vacation time to attend workshops to develop their own skills. They don’t do all this for the money, I assure you. They do it because they care about the education of our children. As another school year comes to a close, it is an appropriate time to thank the effective and dedicated teachers in our schools.

Deborah Stipek is dean of Stanford University’s School of Education.
This article appeared on page E-5 of the San Francisco Chronicle