Dustin Pedroia glanced across the clubhouse toward his star pupil, Will Middlebrooks, who was hunched over his chair at his locker, thumbs tapping away furiously on his cell phone. “What a dork,” Pedroia said, shaking his head in dismay. He had just been talking up Middlebrooks’ aptitude for baseball and how often class is in session for the young third baseman, though with the caveat that it “depends on how the Twitter world is going. If he’s in between tweets, we’ll hang out and talk baseball.” Pedroia means well with his Professor Kingsfield-like barbs toward Middlebrooks. Pedroia talks baseball as well as he talks smack, and he is not the only Red Sox player always willing to lay his baseball knowledge on a student as eager and willing as Middlebrooks. Others, including David Ortiz and Mike Napoli, comprise the All-Star faculty at the Middlebrooks Finishing School. Not yet a full season into his big league career, Middlebrooks is in Advanced Placement classes. “I’ve never been on a team that talks about the game as much as this one,” Middlebrooks said last week before being placed on the 15-day disabled list with back spasms Friday. “I’ve only been on one big league team, but it’s a huge difference from last year — just the focus is a lot better. It’s very easy when you’re on the bench or have a day off to be talking about anything but baseball because a lot of times when you have that off day you flip that switch off and your mind isn’t on baseball. But that’s not the case here.” Middlebrooks provided a case study. In the first game of the last road trip, he came up to bat against Rays closer Fernando Rodney in the ninth inning, with one out, nobody on and the Red Sox down by two runs. Ahead in the count, 2-0, Middlebrooks saw what he thought was a “borderline pitch, probably a strike, middle-in, it had good sink.” He swung right through it, the first of three strikes in the at-bat. The Sox lost. That night in the club’s hotel, Pedroia pulled Middlebrooks aside. Rodney’s pitches have so much movement, Pedroia told Middlebrooks, that if he throws it down the middle, don’t bite — it’s going to break off the plate for a ball.