They don't stand in front of a class 6-7 hours a day. The scam is that they actually teach usually less than 4 hours a day.
Put up, or shut up. I am standing in front of High School classes for 5-6 hours a day (ever heard of "block-scheduling"... and that's not counting the after-school remediation to get the kids prepped for the state tests at the end of the year, for which I get paid nothing). Now provide the evidence for your statement. Oh, and I make 1/3 of the numbers thrown around in this article, and had a 100% pass rate on the state SOL last year (and a 95% the year before).
The problem is that teaching salaries are assigned by seniority, not performance (so the teacher down the hall that's doing nothing gets paid much more than I do simply because she's been there 10 years longer). Consistent performance is what should be rewarded, not longevity. But considering how many people in this world have earned their salaries via longevity, as opposed to what they actually produce in their job, I think a lot of people on here are throwing stones in glass houses...