Give all the teachers a 40% raise

That's what an op ed in Tuesday's Wall St Journal calls for.  The writer seems to feel that teachers ought to get paid more, to bring their salaries in line with say civil engineers.  OK, nice thought and all.  But.
   I'm still a believer in capitalist free market theory.  You pay enough to attract the people you need, and no more.  The modest wages paid to teachers are a signal to young people that we have a goodly supply of teachers and you could do better and make more money in other lines of work.  That's what the market is supposed to do, issue price signals to workers and suppliers, when there is a shortage of something, be it Hershey bars or school teachers, the price goes up, more people take up teaching, or candy companies make more candy bars.  It's a system that has served us well, allocated labor and capital intelligently, and given us fantastic prosperity.  The Soviets tried to operate without the market and they only lasted 70 years. 
   The same op ed did note that teachers of math and science, who are always in short supply, get paid more than the average teacher.  Hint to aspiring teachers, do a math or science major in college rather than the ed major.
   I guess my other problem with the mare 'em more idea is that we have poured more and more money into public schools.  The vast funding increase has not improved our children's education, at least by objective measures like test scores.  They have remained flat over the decades while school funding has doubled.