At one point or another, we all had that teacher who demanded more and saw something in us that we could not, or would not see, in ourselves. Good enough wasn’t good enough, and the papers were often handed back covered in red ink. It may have been tough then, but that teacher may welcome your thanks today for setting a higher bar. Today is National Teachers Day, a time to look at the profession and the challenges faced by today’s teachers. Dennis Van Roekel is the president of the 3 million-member National Education Association, who hopes teachers will hear from former students today.