[anigbrowl]

I disagree, although I think many of your observations are valid. It's unfortunate that our politics have become so polarized that both critics and defenders of teachers often wind up talking past each other.

There are obvious downsides to a seniority system. Younger teachers tend to get offered poorer contractual terms during collective bargaining, be handed the worst assignments (when they have the least experience), and are sometimes even bullied by older teachers with much greater authority and job security. I feel this is true of seniority systems in general, but in education the potential consequences have particularly wide-ranging implications for society. While we don't want to lose skilled veteran teachers, we don't want to raise the barriers to entry too high for new entrants to the profession either. Over longer periods, that leads to a succession problem.

I'm less convinced by your argument about monopsony. You mention that there are thousands of employers in cities (plural) for software engineers, but then refer to a single public school district with a handful of private schools, as if teachers were chained to the first city they work in. On the other hand, there are about 6 million teaching jobs in the US, vs. maybe a million software engineering jobs (going by memory from BLS data). And since, as you say, k-12 education necessarily involves a fairly low student-teacher ratio, the demand in that job market is very predictable based on demographics. While instructional methods may be disrupted by technology (and ought to have been disrupted far more than they have been up to now, if you ask me), a good part of junior education is about social skills and learning to find and function as part of a non-familial social group. Even if we could put a holodeck in every classroom tomorrow along with all other pedagogical disiderata, teachers would still be needed to manage kids' behavior and needs in more or less the same proportions as today. I think that number can be a bit higher than 20 (I grew up with class sizes of closer to 30, and it was fine), but there are only so many children that an adult can supervise and assist effectively.

[earl]

re: monopsony -- You didn't read my comment carefully. Teachers obviously aren't chained to a city, but not all of us are 20 years old and eager to hop around the country. Once you do things like buy a house / apartment, or have an SO with a job, or kids in school, or a group of friends, or family, or get divorced and are forbidden by court order from moving your child around, or have an underwater mortgage, or just plain like where you live, you stop wanting to move. Having one dominant and maybe one or two small alternate (and who knows what their labor demand is) local employers would discourage me or I'd think most reasonable people from wanting a career in a given field. Employment at will is a fine theory when there aren't monopoly / monopsony effects and both buyers and sellers have little leverage and are price takers. Remove that and people naturally see protection.