There are achievement gaps and then there are achievement gaps. A Japanese elementary school teacher with decades of experience was fired this month for repeatedly failing a writing exam designed for his students. According to an Osaka education official, the teacher had been placed in a training program to improve his teaching skills in March, but "failed to show any signs of improvement. Generally speaking, one would hope a public school teacher can pass a [writing] test for grade-school children." Generally, yes.
"Teacher fired after flunking his students' exam," Pakistan Daily Times, November 27, 2004