"Harvard Education Letter" is published bimonthly at the Harvard Graduate School of Education. This issue of "Harvard Education Letter" contains the following articles: (1) (In)formative Assessments: New Tests and Activities Can Help Teachers Guide Student Learning (Robert Rothman); (2) Recent Research on the Achievement Gap: How Lifestyle Factors and Classroom Culture Affect Black-White Differences; and (3) Three Thousand Missing Hours: Where Does the Instructional Time Go? (Richard F. Elmore). Online version may contain additional articles.