The adoption of state accountability testing in the 1990s coincided with the movement of some school start dates from September into August. Using data from Wisconsin, this paper connects these phenomena, showing that some low-scoring districts advanced their school start dates to allow their students more time to prepare for exams. I use a 2001 Wisconsin state law that restricted districts to start dates after September 1st to identify the effects of this extra time on student achievement. Extra classroom days are associated with small increases in Math scores for 4th graders, but not average reading or language scores. Extra classroom time may also have increased third grade reading scores for students in the upper portion of the ability distribution.