Teachers, per-pupil spending and student achievement

[Update: Many thanks to Louis F. Caruso for pointing out in a comment on this post that student achievement, whether flat or not, is all about shifting demographics.  I should have known that student achievement was largely about students, not schools!  Caruso mentions increasing ELL and SE students; after a quick look into the matter, it seems like other demographic shifts may be significant as well. In any case, the supposedly "flat" student achievement is, while understandable for the reasons I discuss below, also not as flat as it may seem on the surface.]

American schools have spent more per pupil since the 1970s without seeing a proportionate improvement in student achievement.  Many proponents of "education reform" cite this fact as evidence that (A) our schools are failing, and that (B) we need to destroy teachers' unions. This doesn't make sense; here's why:

Yes, we have been spending more per student and seeing few achievement gains:

Below is a graph used by Bill Gates a couple of years ago. This graph is pretty similar to other graphs used by other Ed Reform types (see graph #3 here); it shows per pupil expenditure doubling since the 1970s, and NAEP scores not changing much.



This is a somewhat dubious graph, since it looks like there might be SOME improvement in the test scores, and the Y-axis scales are not necessarily comparable.  But let's grant that okay, we have spent more money without getting much improvement.  Now why would this be?  The answer Gates has generally given, and that Ed Reformers give, is that bad teachers and obstructive teachers' unions are getting in the way of improvement.  This strikes me as wrong for three reasons:

1. Teachers and kids are not getting better from century to century and decade to decade (there is no Moore's Law for teachers and children)

2. Even though teachers should be making more money, to share in the national wealth, in fact they are not--salaries have been flat since the seventies!

3. Therefore, the increase in per pupil spending has been in other areas--but what?

No wonder students and teachers haven't improved much: people are not like microchips 

Teaching, like parenting or art, takes just as much time as it always took, and is not necessarily better now than a generation ago.  It takes many fewer people-hours to make a computer than it did in 1975, and the computers we make are of dramatically better quality, but the art that we make, or the children that we raise, are not so dramatically better.  Maybe they're a little better, but they're not dramatically better.

Some things have gotten better:

Standard 1970s computer

Standard computer today

But some things have not gotten better:
                                       

Bobby Orr

Brad Marchant

People are not computers. To ask Brad Marchant to be a better hockey player than Bobby Orr, or a better sportsman, is absurd; to ask today's poets to be better than Larkin or Ashbery is absurd; and to ask today's teachers to be better than, say, my mom, is equally absurd.

Our national income has gone up, so teachers' incomes should have gone up, too... 

Over the thirty-plus years that Gates's graph covers, America has gotten much, much richer. One way to measure how rich we are is GDP; in order to adjust for an increase in population and for ups and downs in how many hours people work, we can use GDP per hour worked.  By this measure, America nearly twice as rich now as in 1975.





If the national income has gone up a lot, then you might imagine that teachers, like hockey players, might get paid a bit more, even if we aren't much better than our 1975 counterparts.

...but, amazingly enough, teachers' salaries have NOT gone up!

According to the National Center for Education Statistics, a high school teacher in 1973 made, in 2007 dollars, $51,961  In 2007, the average high school teacher made $52,367.  Teacher salaries have been flat for over 30 years, despite the remarkable GDP growth we've seen.

Teachers are not alone. Wages in America, except for the top 10% or so, have been flat for decades.  The country has gotten much richer, but the overwhelming majority of workers have not shared in this prosperity.  Here's a graph showing growth in GDP/hour worked ("productivity") and in hourly compensation for non-supervisory workers; you can see the divergence between GDP and wages, starting in the early 70s:




So even though teachers SHOULD be making more money, we're not.  This certainly begs the question of what that extra money has been spent on.  I'm not a school finance expert, but you'd think people like Bill Gates might be able to figure it out.  If he hasn't, this is another pretty good argument for his not being in good faith.  He sends his kids to their fancy private school, which no doubt has the same exact dynamic going on (rising per-pupil costs, flat student achievement numbers and flat teacher salaries), but it never occurs to him that maybe his attacks on teachers are fundamentally wrong?  (It's nice to see him, in his 4/3 WaPo piece, trying to be more diplomatic, but he has no credibility.)

Update: On second thought, I shouldn't have said that the WaPo piece was nice.  Anthony Cody is right; that Gates is pompously criticizing an over-reliance on test scores is outrageously hypocritical, given that Gates has arguably the largest individual responsibility for our current testing mania.  But then, this is a guy who without a glimmer of irony has a Gatsby quote about failing to reach your dreams engraved in the library of his Gatsby-esque mansion.