January is preschool open house season, and parents with the wherewithal to be picky have lots of criteria to think about. In Silicon Valley—home to public schools that produce some of the best test scores in California—hoards of moms and dads are likely narrowing down their myriad options as they tour campuses, review guidebooks, and consult with fellow parents. The area reflects the degree to which American parents have become obsessed with ensuring their kids have an academic edge by the time they start kindergarten. It also reflects the growing national reality that the children born to low-income immigrants are typically among the children who get left behind: Close to three-quarters of Silicon Valley’s poor preschool-age kids have at least one foreign-born parent, and thousands of them enter kindergarten without any prior formal education.