It's widely accepted as gospel in America that teachers aren't paid "enough", even though nobody really can tell you what would be fair. If a teacher agrees to his salary, then it is fair. If the salary wasn't their best option then the teacher would do something else.
As a Lieutenant Colonel in the Army I made less in terms of salary than my kids 2nd grade teacher. They get paid more than enough.
For proof I look at the private and charter schools that are not controlled by the teacher's union. They pay their teachers about 25% less than the public school teachers, but have no trouble filling their vacancies and retaining skilled educators.
The public schools have to find a way to balance out the teacher's unions and have to find creative ways to increase parental interest and family involvement in the overall educational process. It takes strong leaders to turn things around and that is a huge problem for most public school districts--most principals are poor teachers who couldn't succeed in the classroom so they took the tuition money guaranteed in their contract, earned their administrator degree and moved up to a leadership position. There is not any sort of real process that identifies potential leaders, selects them for developmental training and promotes them--it is all self selection and leadership by default.
An example of success that I've seen happened a few years back in Hawaii.
My 2nd oldest graduated from a public school in Hawaii that traditionally had a lot of challenges with discipline, attendance and academic performance. They did pretty well in sports but that was about it. Then they got a new principal who set up a vision that he called "Ohana, School, Sports." What this meant was in priority order you had Family (Ohana), then your academics, then your sports. Enforcing this standard did an amazing turn around for the school. Hawaii is very family oriented, so by placing the family first, he spoke to one of the central values of most of the community. Then he made the kids take responsibility for keeping their grades up. For example, if you played a sport, it was the student's responsibility to get a weekly progress report signed by all of his/her teachers that confirmed you had turned in all of your homework and were passing all of your classes. Most other schools I've seen require you to pass your core subjects only and also require the teacher to let the coach know if someone is failing. At this school, if the starting quarterback didn't get his sheet signed on Friday, he didn't dress out.
We tried to get our school district here to adopt a similar weekly grade check but were nearly laughed out of the building!