From Muppet Wiki

Mr. Moses is the world's first teacher, appearing in a Sesame Street News Flash when he is interviewed by Kermit on the first day of school. The bearded caveman pioneered classroom principles and with the help of Kermit founded such classroom rules as students must sit down, students should be quiet during a lesson and students should raise their hand and answer one at a time. The first lesson he teaches his students (including Oog, Argh, and Runk) is on the letter n and n-words.