“Governor [Mitt] Romney doesn’t think we need more teachers,” President Obama said last night. “I do.”

The President’s confidence that “we need more teachers” to improve education is misplaced, and his proposal to subsidize teacher hiring using federal dollars would do more harm than good.

Adding teachers is intended to reduce class size. It’s worth pointing out that the national student–teacher ratio is already historically low, according to projections by the National Center for Education Statistics. Nevertheless, class size reduction does not produce reliably higher student achievement.

Smaller classes may help particular students with particular socioeconomic backgrounds at particular times in their lives with particular kinds of teachers teaching a particular kind of curriculum. In general, however, the benefits of class size reduction to the average student are small to nonexistent, and no reasonable cost-benefit analysis endorses class-size reduction as a general policy.

But subsidizing teacher hiring would be more than just an inefficient use of federal tax dollars. It would essentially be a bailout of states and localities for their fiscal irresponsibility. The average public school teacher already receives a total compensation package (wages plus benefits) that is above fair market levels, and this overly generous compensation is part of the reason that teacher layoffs and cutbacks were necessary in the first place.

So while “more teachers” may sound like a wonderful reform in the abstract, the proposal carries little to no public benefit, while helping to perpetuate irresponsible budgeting at the state and local levels.