Despite billions of dollars and massive efforts on the part of thousands of highly dedicated and intelligent people over the past 25 years, the size of the test-score gap between the wealthiest and the poorest students has not changed. These problems do not end at high school. Studies suggest that students with low test scores are less likely to pursue higher education, obtain and keep jobs, provide for their families, exercise their civic rights and responsibilities, and lead fulfilling lives. Education is supposed to enable everyone to do those things. It represents the best hope for breaking the cycle of multigenerational poverty. [This article is an excerpt from the author's book, "The Knowledge Gap: The Hidden Cause of America's Broken Education System--and How to Fix It."]