The trouble is, researchers Mary Beth Walker and D. Mark Anderson have yet to pin down the exact reasons why a four-day school week has this beneficial academic side effect. In "Does Shortening the School Week Impact Student Performance? Evidence from the Four-Day School Week," they speculate that "improved attendance, increased teacher job satisfaction, and better teaching methods" could be responsible for the test score boosts. The researchers' data didn't allow them to distinguish between schools that used the fifth day for planning and collaboration and schools that didn't take advantage of the extra time, but their future reports will hopefully shed light on the situation.
Before more districts adopt this policy and have to decide whether some or all teaching staff should try to use that fifth day, it sure would be nice to know whether the amount of time allocated for collaborative planning by teachers is a relevant factor in explaining these changes in student performance.