Teaching doesn’t attract highly paid workers because in addition to a big pay cut those workers would be considering likely worse working conditions as well.
If teaching is low-status it is no wonder that education standards are low and thus educational achievement is low, as they note in the article. The alternative is failing most students and having a labour supply problem. In my country, Australia, you occasionally see news articles describing some shockingly bad final year high school scores (ATAR scores) being accepted into teaching degrees. Unfortunately, the fact that this happens further entrenches teaching as low status and puts downward pressure on the minimum bar for ATAR scores.
Remarkable, but unsurprising, that the Heritage foundation then suggests _lowering_ wages even further. You’ll get even worse candidates heading for teaching and they may even be able to next time show the same 9% positive bump.