In yesterday’s Wall Street Journal, George W. Bush Institute fellow Jay Greene argues that expanding the number of teachers in the U.S. education system is an ineffective and expensive waste of precious school funds. Unfortunately, his weak analysis makes this article an unreliable resource for anyone interested in changing how schools use their own resources.

Greene states:

"For decades we have tried to boost academic outcomes by hiring more teachers, and we have essentially nothing to show for it. In 1970, public schools employed 2.06 million teachers, or one for every 22.3 students, according to the U.S. Department of Education's Digest of Education Statistics. In 2012, we have 3.27 million teachers, one for every 15.2 students.... [Despite employing more teachers,] math and reading scores for 17-year-olds have remained virtually unchanged since 1970."

Part of that is right. An examination of the U.S. Department of Education's most recent study of long-term trends in U.S. education (released in 2008) reveals that 17-year-olds' scores remain largely unchanged from 1971 to 2008. However, the same data shows notable academic gains have been made among 9- and 13-year-olds. In fact, during the same 1971 to 2008 time period the average reading score for 9-year-olds rose 12 points (from 208 to 220). For 13-year-olds over the same period, the score rose 5 points (from 255 to 260).

In math, the 9-year-old's average score rose 24 points from 1973 to 2008 (from 219 to 243). The 13-year-old's average score rose 15 points over the same period (from 266 to 281), but the 17-year-old's average score only rose 2 points (from 304 to 306).

Using 17-year-olds' test scores as evidence of national academic stagnation ignores the gains made in younger age groups, undercutting Greene's argument-which might be why he ignored them.

Where the Greene piece really loses strength is assuming the low changes in 17-year-olds show the failure of small class size. At most his argument shows correlation, and it is far from proving causation. For instance, it is quite plausible that the discrepancy in test scores is related to efforts to reduce class sizes in earlier grades. According to the Center for Public Education, most programs to reduce class size take place in earlier grades "because earlier research... suggested that these are the optimal years for such programs." This may be evidence favoring the hiring of more teachers to reduce class sizes. Unfortunately, Mr. Greene's article lacks the necessary depth to even acknowledge this intriguing possibility, preferring the glib use of statistics to support a superficial analysis.

If it turns out that more teachers really are the best approach to changing education, this does not mean the federal government should fund them. In a best-case scenario, the expansion of private schools would provide that influx of new teachers.