Dean had an honest to god blackboard! Sam had no idea where he had gotten it from (probably the bowels of the Bunker). He used it when he was teaching.
Yeah, Dean taught.
He taught Ben (things that schools never would like how to wield a gun, what each monster is and so on).
He taught Cas (how to be human, how to cook, how to clean and so on).
Sam had walked in on a lesson with Cas once, or Sam thinks that's what he walked in on. It was a little hard to work out. On the blackboard Dean had drawn a series of different tools, a spanner, a hammer, a wrench among others, with the title 'DIY' at the top. Sam had no idea how DIY had prompted a, rather heavy from the shirtless and rumpled state the pair were in, make out session.
To be honest he really didn't want to know, and really it was getting old walking in on their make out sessions all over the place. "Having a good lesson?" Sam asked before walking past and heading for the showers. He didn't see Dean's sultry look at Cas as the angel turned bright red.
Sam was just glad Ben was at school.