IN recent years, we’ve been treated to reams of op-ed articles about how we need better teachers in our public schools and, if only the teachers’ unions would go away, our kids would score like Singapore’s on the big international tests. There’s no question that a great teacher can make a huge difference in a student’s achievement, and we need to recruit, train and reward more such teachers. But here’s what some new studies are also showing: We need better parents. Parents more focused on their children’s education can also make a huge difference in a student’s achievement.

How do we know? Every three years, the Organization for Economic Cooperation and Development, or O.E.C.D., conducts exams as part of the Program for International Student Assessment, or PISA, which tests 15-year-olds in the world’s leading industrialized nations on their reading comprehension and ability to use what they’ve learned in math and science to solve real problems — the most important skills for succeeding in college and life. America’s 15-year-olds have not been distinguishing themselves in the PISA exams compared with students in Singapore, Finland and Shanghai.

To better understand why some students thrive taking the PISA tests and others do not, Andreas Schleicher, who oversees the exams for the O.E.C.D., was encouraged by the O.E.C.D. countries to look beyond the classrooms. So starting with four countries in 2006, and then adding 14 more in 2009, the PISA team went to the parents of 5,000 students and interviewed them “about how they raised their kids and then compared that with the test results” for each of those years, Schleicher explained to me. Two weeks ago, the PISA team published the three main findings of its study:

“Fifteen-year-old students whose parents often read books with them during their first year of primary school show markedly higher scores in PISA 2009 than students whose parents read with them infrequently or not at all. The performance advantage among students whose parents read to them in their early school years is evident regardless of the family’s socioeconomic background. Parents’ engagement with their 15-year-olds is strongly associated with better performance in PISA.”

Schleicher explained to me that “just asking your child how was their school day and showing genuine interest in the learning that they are doing can have the same impact as hours of private tutoring. It is something every parent can do, no matter what their education level or social background.”