Any episode with flashbacks to Sam and Dean's childhood is always a special one. Illustrating how far they've come how much they've changed and how much they've stayed the same. This one was no exception. And let's face it - any time that we get to delve further into the relationship between the two brothers is always a good time. They are, after all, the reason we are watching. So these episodes which luminate and really focus on that bond are a payoff. In many ways they are as critical to the show as what we term 'mythologically driven' episodes which are full of twists and turns. It gives the show depth and meaning. At least, that's my thought on it.
But Sam and Dean in my high school? I would have been friends with Sam. I was a complete theatre-obsessed High Schooler that had a bunch of friends but no "group" of friends - and I hated the kids that would talk back to teachers or cause a ruckus in class or thought they were really cool ... which is kind of teenage Dean. I can honestly say I probably would have found Dean annoying in High School. I wouldn't have hated him, just ignored him. Sam I would have found interesting because he was quiet but not really shy, smart, nice to the teachers and seemed keen to do his work.