Nothing, of course, about how to pay for it, or what it would look like, or how it would affect collective bargaining, or whether it would be a huge unfunded mandate... Golly, if I were cynical, I would have thought this was just slapped together to distract us from something!
But let's put all that aside and ask a simple question: will it work? Is there a correlation between the length of the school day and student achievement? Luckily, we can go to the NJDOE and look at the data files - because schools are required to report both the length of their school day and the amount of instructional time their students receive. Let's see if there's a connection by starting with this:
So what we have here is a scatterplot that shows the relationship between two variables: how many 8th graders in a school are "above proficient" on the state's annual math test, and the percentage of students in the school who qualify for the federal free lunch program - the best proxy measure we have for economic disadvantage. Each dot is a school: where it lies on the graph depends on the two variables.
See what happens? In general, as a school's free lunch eligible (FL) percentage goes down, the percentage of 8th graders who pass the state test goes up. Obviously, poverty affects student learning: the dynamics are very clearly understood.
In geek terms, that "R-squared" number in the bottom corner tells us that about 57% of the variation in the proficiency rate is "explained" by the FL rate. You can see how that red line, called a "regression line," gives us a pretty good prediction of what a school's proficiency rate would be if we knew what its FL percentage was.
Now, for comparison, let's see if there is a similar relationship between the length of particular school's day and its proficiency rate on the 8th grade math test:
In the previous graph, there was a fairly strong relationship between FL and test scores; but here, we see that there is no practical relationship between those same test scores and the length of the school day. See how much smaller the R-squared number is? It's telling us that even if we knew the length of a school's day, it would be nearly impossible to predict how that school did on the 8th Grade math test.
And what about instructional time - the amount of time students are actually learning?
In New Jersey, there is no correlation between the time a school's students are in class and how many students pass the state test.
If Chris Christie really wanted to increase test scores, he wouldn't propose lengthening the school day; he would propose a way to lift every child's family out of poverty.
So why would he bring up this useless idea today? Thinking...
h/t the always excellent Rob Tornoe
Note: I only included schools that had more than a five hour school day so as not to corrupt the results with some outliers. There are a few schools in New Jersey, apparently, that have very short school days; they may serve special populations, or only have part-day Pre-K and K programs. Just keepin' it real, folks.