When you underpay teachers, people who hate teaching, and hate being teachers, will become teachers because all the people that had better options did something else.
And then you will have people who absolutely love teaching, and are willing to live in poverty to do so, speckled around that cess pool of mediocrity. It reminds me of high school actually.
That means overpayment is wrong and underpayment is wrong.
Teachers should be paid the correct amount, no more and no less.