K-12 teaching should require master's degrees in my opinion. And that should bump up the salaries. I'd say the national average should be around $50k starting out, $100K or so towards retirement. With salaries higher in urban areas with high cost of living and a bit lower in rural areas where it's dirt cheap.
And again with the "summers off" bullshit. Any decent teacher is working 40 hours a week most of the summer with redoing lesson plans, attending training seminars and meetings etc.
And the higher pay should come with more accountability for teachers, thus giving them more incentive to work through the summer to make sure they are doing the best possible job in the classroom.
The key thing right now is it's a high stress job with a lot of pressure to have your students hit test scores, all the bullshit of dealing with parents and administrators etc., and just doesn't pay well relative to that. You can get lower stress private sector jobs that pay as much or more, and that's why the turnover rate is so high.
Improving our education is the number 1 key to the US having any chance of remaining the world leader in innovation and the world economy. It's not going to happen if we don't find ways to attract a lot of the best and brightest students to go on to be teachers. As the turnover rates etc. show, we're not doing that now. There's little incentive to go be a teacher vs. going to law school or med school or an MBA program etc. And even if you want to teach, going on to a PhD and working as a professor is going to be more lucrative with starting salaries ranging from around $55K to $80K depending on field, area and school, with ending salaries over $100K in most fields, and well over in some like the hard sciences. Of course it comes with more stress than a K-12 job with the publish or perish pressure and the pressure to land grants, so it is a trade off.
But in any case, the key to saving education is getting bright people interested in being teachers, and one thing that has to happen for that to occur is getting salaries up so they're attractive relative to private sector jobs.