The Evidence for Pre-K and Kindergarten Excellence
A week or two ago, the New York Times featured a story regarding recent educational findings by a group of educational researchers about the effectiveness of good kindergarten. The researchers were re-examining individuals who had taken part in the rigorous 1980′s educational experiment in Tennessee called Project STAR. First, a little about the project:
The Student/Teacher Achievement Ratio (STAR) was a four-year longitudinal class-size study funded by the Tennessee General Assembly and conducted by the State Department of Education. Over 7,000 students in 79 schools were randomly assigned into one of three interventions: small class (13 to 17 students per teacher), regular class (22 to 25 students per teacher), and regular-with-aide class (22 to 25 students with a full-time teacher’s aide). Classroom teachers were also randomly assigned to the classes they would teach. The interventions were initiated as the students entered school in kindergarten and continued through third grade.
The analysis of academic achievement consistently and significantly (p<.01) demonstrated the advantage of small classes over regular size classes and regular sized classes with a teaching assistant. As Jeremy Finn and C.M. Achilles stated in the American Educational Research Journal (Fall 1990), “This research leaves no doubt that small classes have an advantage over larger classes in reading and math in early primary grades.” Tennessee’s Project STAR was featured in the American School Boards Journal in May, 1992 and in many different periodicals since.
There are a few things to note here: 1) the study was longitudinal, done over the course of three years (though the particular students involved were visited time and again, later in middle school, high school, and now in their 30′s), 2) the study was experimental, with random assignment of students, which is accepted by most researchers as the gold standard of educational research. Over the years, a number of different studies have been made of this cohort of students, finding, significantly, that test score gains did due to the small class intervention not stay with the students through middle and high school. That’s not a huge surprise, and is pretty similar to the findings of the Pre-K studies periodically emanating from the Tennessee Comptroller from time to time.
However, news out of the STAR Project is incredibly encouraging for the long-term impact of early interventions. Via the New York Times:
Early this year, Mr. Chetty and five other researchers set out to fill this void. They examined the life paths of almost 12,000 children who had been part of a well-known education experiment in Tennessee in the 1980s. The children are now about 30, well started on their adult lives.
On Tuesday, Mr. Chetty presented the findings — not yet peer-reviewed — at an academic conference in Cambridge, Mass. They’re fairly explosive.
Just as in other studies, the Tennessee experiment found that some teachers were able to help students learn vastly more than other teachers. And just as in other studies, the effect largely disappeared by junior high, based on test scores. Yet when Mr. Chetty and his colleagues took another look at the students in adulthood, they discovered that the legacy of kindergarten had re-emerged.
Students who had learned much more in kindergarten were more likely to go to college than students with otherwise similar backgrounds. Students who learned more were also less likely to become single parents. As adults, they were more likely to be saving for retirement. Perhaps most striking, they were earning more.
All else equal, they were making about an extra $100 a year at age 27 for every percentile they had moved up the test-score distribution over the course of kindergarten. A student who went from average to the 60th percentile — a typical jump for a 5-year-old with a good teacher — could expect to make about $1,000 more a year at age 27 than a student who remained at the average. Over time, the effect seems to grow, too.
There is some REALLY excellent and intriguing stuff in the presentation [pdf] — the correlation between small class sizes and income, as well as teacher experience and effectiveness. One intriguing thing for me was the graph charting teacher experience versus eventual earnings of their students:
As you can see, earnings are plotted on the left, with teacher experience along the bottom. The mean line (in red) is plotted through the middle. The important thing to remember here is that the mean line is drawn by the computer. A “line of best fit” will be drawn through whatever data exists, no matter how random it is. Here’s an example I created:
As you can see, the data points I entered are completely random, which means that, even though there’s a positive line, it doesn’t really mean much. It’s just the computer using statistical regression to find the “average” line through the noise. I made the chart at this site, which is an excellent one for understanding the basics of scatter plots and lines of best fit. Check it out!
On the other hand, there are several charts in the report that show a strong (and natural) correlation (this one presents college quality versus test scores, where higher test scores predicts that you go to a higher-quality college):
I mention this because, to me, the experience/earnings graph in the researchers’ report seems to exhibit this kind of weak correlation, which is interesting. Yes, there is a positive trend line, meaning that, on average, a teacher with more years of experience means that their students will earn more, eventually, but it is a very weak correlation. That means to me that teacher experience is not a huge predictor of success. This is in DIRECT contradiction to the assumption underlying the typical single salary schedule which raises pay/rewards teachers almost SOLELY based on experience. If years of experience don’t have the effect on student achievement (or life outcomes), then its questionable as to why we should reward JUST based on experience (as opposed to training, student achievement/outcomes, leadership, etc.). For interesting discussions of the single salary schedule, its implications, and its alternatives, check out two very respected educational academics, Michael Podgursky [pdf] and Eric Hanushek, on the subject.
Understand, now, that I’m not saying experience doesn’t matter. It’s very well established that for a first few years, teacher experience correlates very strongly with teacher effectiveness. Simply put, you learn a LOT about how to teach in your first few years as a teacher. Check out this paper from the Brookings Institution on the subject. However, these effectiveness gains based on experience tend to level out after just a few years. Whether that’s a failure of our professional development system (I think that it’s definitely a part), or whether you simply learn pretty much most of what there is to learn as a teacher after 5 years or so is debatable. I’d contend that research like this, pointing to the incredible development power of experience (learning by doing) is also a critique of the teacher preparation system — if you learn most of what it takes to be a good teacher while on the job, does it really make sense to require a full-on 4 year degree to start teaching? Of course, this is tied in to the whole debate about alternate certification and, among other programs, Teach for America. A topic for another post.
Of course, another chart in the presentation is just as compelling, and presents somewhat of an opposite finding:
Here you can see that having a more experienced teacher (greater than 9 years experience versus less than 9 years experience) does have an impact on future earnings, and a sizeable one at that (almost $1000). Just goes to show you that data can show you very different things, depending on how you analyze and present it.
At any rate, here’s the main point: Despite the fade-out in test score gains attributable to early interventions, such interventions DO in fact have measurable positive effects later in life. I’m lumping Pre-K in here as well, even though the study was actually about small-class kindergarten interventions, because I think they two programs have similar effects. Just goes to show you what I argued before: Just because the fade-out in test scores happens over the course of a few years does not mean that Pre-K isn’t effective. Don’t believe people who tell you otherwise: Pre-K, and early childhood interventions like it, can pay wonderful dividends down the line. Just because our clunky tests (which we know suck, and are only now starting to get better) can’t measure it, doesn’t mean there isn’t an impact.