Many aspects of pre-k programs affect their quality. “Quality” in turn affects the magnitude of economic development benefits for a state or local economy. I’ll be exploring this important issue of pre-k quality in several blog posts.

One of the most controversial quality issues is the issue of teacher quality.  Teacher quality is a controversial issue because a lot of money is at stake, and it affects people’s jobs. Potentially, measures to increase teacher quality in pre-k education could significantly increase both pre-k teacher pay and pre-k program costs.  Requiring particular teacher credentials could threaten some current pre-k teachers’ jobs. Some teacher quality policies might affect how pre-k teachers are evaluated.  (For example, test scores at entry to pre-k and entry to kindergarten could be part of the evaluation.)

Susan Ochshorn of ECE PolicyWorks explores this issue of teacher quality in a recent blog entry at Huffington Post.   She points to recent research by economist Raj Chetty of Harvard (along with colleagues  John  Friedman, Nathaniel Hilger, Emmanuel Saez, Diane Whitmore Schanzenbach, and Danny Yagan) that uses data from the Tennessee Class-Size Study to show that higher teacher quality in kindergarten raises earnings of former kindergartners at age 27.

Chetty et al show that higher test scores in kindergarten are significantly correlated with adult earnings at age 27. Interestingly, these adult earnings effects occur even though test score gains in kindergarten tend to fade later in K-12.  By first grade, over 75% of the kindergarten test score gains have vanished, and by fourth grade, the kindergarten test score gains have completely disappeared. However, their estimates suggest less fade-out in effects on various behavioral measures in grades 4 and 8. These better “non-cognitive skills” or “soft skills” (see my earlier blog post on soft skills) may explain the long-term effects of better kindergarten experiences on adult earnings.

Chetty et al use their results on kindergarten test scores and adult earnings, together with previous research on how teacher quality affects kindergarten test scores, to calculate the adult earnings effect of a specified improvement in kindergarten teacher quality.  For example, consider a “1 standard deviation” improvement in kindergarten teacher quality. This corresponds to changing from the “median” kindergarten teacher to a kindergarten teacher at the “84^th percentile” of teacher quality, that is from a teacher who is better than half of all kindergarten teachers, to a teacher better than 84% of all kindergarten teachers.   For a kindergarten class size of 20, this increase in teacher quality is estimated to increase the present value of future earnings of these former kindergartners by $214,000.

As Susan Ochshorn mentions, these high effects of kindergarten teacher quality on adult earnings also suggest the importance of teacher quality in pre-k programs and child-care programs.  Surely if teacher quality is so important at age 5, it should be of considerable importance at age 4 and younger ages.

In chapter 5 of Investing in Kids, I take a somewhat different approach to estimating the importance of teacher quality. I ask the following question: suppose we increase lead teacher salaries in pre-k from what are typical salaries for an individual with a high school degree plus a Child Development Associate credential, to typical salaries for a public school kindergarten teacher. How much would learning in a one-year pre-k program at age 4 have to go up for the local economic development benefits from this change to exceed the increase in program costs?

I take the pre-k salary figures for teachers with different credentials, and pre-k program costs, from the excellent publication by Barbara Gault and her colleagues at the Institute for Women’s Policy Research, Meaningful Investments in Pre-K: Estimating the Per-Child Costs of Quality Programs (2008). Gault et al calculate annual straight salaries, in 2007 dollars, before payroll taxes and benefits, at about $18,000 for a lead teacher with only a CDA credential, versus $45,000 for a lead pre-k teacher who is paid similarly to a typical public school kindergarten teacher.  Based on that research, I calculate that these higher salaries end up increasing pre-k’s cost per student by a little over one-fourth.

I use estimates that are similar to Chetty et al for how early test scores are related to adult earnings. Based on these estimates, I conclude that these higher teacher salaries “pay off” in higher economic development benefits even with only very slight effects on student learning in pre-k programs.  Student learning gains must only go up by 5% compared to typical student learning in pre-k for this salary increase from $18,000 to $45,000 to pay off in higher present values of earnings per capita in a state’s economy.  This calculation adjusts the effects downward to account for former pre-k students who move out of state as adults.

Now, there is certainly room for debate on how such improvements in pre-k teacher salaries should best be used to improve pre-k teacher quality. How much of that increase in teacher salaries should be used to allow for higher credential requirements in terms of education and training? How much of that increase in teacher salaries should be used to allow for stronger evaluation of pre-k teachers by programs based on student outcomes or other mechanisms?  I suspect that as we explore how to improve teacher quality in pre-k, we will find that both increases in credentials and strengthening of evaluation will be helpful in improving pre-k teacher quality.  And higher salaries may be a part of a personnel policy that will allow for more selective recruitment and retention of pre-k teachers, and will reduce the problems caused by teacher turnover.

However, the underlying point should not be forgotten. Early learning is so important to adult success that even very slight improvements in early learning can justify large costs incurred to increase early learning.  Even modest improvements in early learning, whether due to higher teacher credential requirements, or stronger evaluation procedures, can justify the considerable costs that may be needed to implement these reforms.