In K’s case proof of his good behavior was that he kept his “green card” all day. In his first grade class each child starts out with a green card by their name on a big board. If they misbehave then the green card is pulled and behind it there is a yellow card. If they do something else wrong then the yellow card is also pulled and behind that is an orange card. The final step is removal of the orange card, leaving the dreaded red card.
Today K kept his green card, and I don’t think that K has ever had his yellow card pulled.