In that scene, Dr. Turner and Shelagh had been measuring Angela and Mai's height when Timothy comes by and tells them he's going around to friends to listen to "A Hard Day's Night" and he's taking some beer he's found in a cupboard with him. Shelagh jokes that she needs to check if he's "tall enough" to drink beer but since he's now taller than her, she kind of indicates she thinks he is. Patrick also observes that Paul McCartney's mother was a midwife.
There's another kind of "companion scene" to that in Episode 2 where Shelagh tells Patrick there's some coffee left if he'd like a cup. He declines, but Timothy pipes up that he'll take it. Shelagh tells him that percolated coffee isn't good for him and that tea is strong enough for a teenaged boy. She then sends him upstairs with the little girls to supervise their brushing their teeth. IOW, beer is fine for a boy his age, but not coffee.