I mentioned recently an idea that could improve education by taking account of how different teachers affect their students’ test scores. Schoolhouse Rock prints an e-mail from a New York teacher pointing out an obvious problem:

During our first standardized test of the year, many hands went in the air. I shook my head at them, because according to the rules, I’m not allowed to talk to them during a test. They were outraged. “Why can’t you help us?” they asked.
We had a class discussion after the exam was over. Every single one of them had received help on state standardized tests in their old school. For some of them, the teacher would explain the questions when they didn’t understand something. Several students had teachers give them the correct answer. One of my students saw a teacher sit down with another student’s test, erase all of his answers, and write all new ones in.

This seems simple enough to me. You could drastically reduce this by simply having each teacher give the test to a different teacher’s students. Or, you could have big groups of students take the test somewhere, like a gymnasium, supervised by multiple teachers — absent a conspiracy involving every teacher present, this would solve the problem completely.