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.