Just to get this out of the way, I like teachers and my daughters have been blessed with some very good ones over the years. Since my girls are 13 years apart in age, I have and will continue to be involved in the K-12 educational system for many years and have dealt with and will continue to deal with a lot of teachers. My youngest started Kindergarten the year my oldest started college so, by the time it's all said and done, I will have been involved in K-12 schools for 26 years in a row (minus the 3 years we homeschooled).
That being said, I completely understand what the teachers are saying about not being paid for summers even if they receive a check during those months. I get it. They are being paid for 10 months of work. The problem I have with it is that teachers tend to express their salary in yearly terms. "I earn $46,000 per year". They then compare that figure to other professional salaries and argue that they are underpaid. In other words, they are comparing part-time work to full-time work when they express their salary on a yearly basis. Now, I am not saying that teachers work part-time during the school year. They do work full-time for ten months out of the year and I don't dispute at all that they occasionally or even often have to put in extra hours during those ten months. That is, however, not any different than most professionals who, in my experience, rarely work solely from nine to five, five days per week. The difference is that other professionals work their hours, including extra hours for which they receive no extra compensation, for 12 months out of the year instead of 10.
I also think teachers tend to forget when discussing their pay that they are one of the few remaining professions that receives a pension. A pension is a huge benefit that a lot of professionals, even professionals with advanced degrees, do not receive. My husband is a professional who is lucky enough to work in a job where he will receive a pension and his employer contributes to his 401(k) as do we. I, on the other hand, am also a professional with an advanced degree and I am required to fund my own retirement and will never have a pension with a guaranteed monthly income in my old age. In other words, a pension is a huge benefit that many teachers do not consider when evaluating their pay because they won't receive the financial benefit for a long time. It is nonetheless a huge financial benefit of the job and one that a lot of teachers do not consider when evaluating their pay.