"Secretary of Education Arne Duncan has voiced a preference for expanding school days and years to increase instructional time over reducing class sizes." -- EdweekWhy do Arne Duncan, Rahm Emanuel and corporate school reformers all favor longer school days and school year while opposing smaller class size initiatives? The answer is simple. The longer school day and year require fewer teachers, with each teacher teaching more kids in larger classes at no extra cost. This is the business model of school reform. Yes, it's cheaper in the short run. It is also a "reform" that is meant to override collective bargaining agreements.
However, there is no evidence that more instructional time alone, especially in larger classes, has any positive effect on measurable learning outcomes or on closing the so-called "achievement gap." In fact, many studies show a drop-off in student engagement that accompanies longer instructional time and that the addition of instructional time alone is insufficient to maximize learning outcomes (See: "Time and learning in the special education classroom." by Libby Goodman). There's plenty of other research showing little benefit expected from a further increase in the amount of math and reading instruction offered per day. For example: The merits of a longer school day, Charles R. Link, James G. Mulligan and Theory and practice of early reading, Lauren B. Resnick, Phyllis A. Weaver.
Ironically, some of the best research summaries on the benefits of smaller class size can be found right on the D.O.E.'s own website. Other resources include: