Our protagonist is the late bloomer in a group of pre-teens of eastern european ancestry -- all the parents are colleagues, professors of math or science at a nearby university. Our protagonist notices that, one by one, each of his friends stays home sick from school for nearly a week, coming back several inches taller, much more interested in academics (and uninterested in their earlier obsessions), and with completely remodeled bedrooms and a completely new wardrobe. He suspects that some of his friends might actually be getting replaced by aliens; his parents dismiss this. After all his friend group has been "replaced", feeling lonely, he suddenly has an insatiable craving for paper. Feeling strange, he stays home; his hair and fingernails fall out, and he can't keep himself from eating them (along with all his clothing and all the books he owns). He begins vomiting a thick foam of fibers, as body parts begin falling off. Feeling like he's dying, he nestles in this bed of fibers. A week later, he emerges, several inches taller and with a greater interest in academics.
(This Cronenberg-does-R.-L.-Stein-does-Invasion-of-the-Body-Snatchers premise is based on an in-joke that used to exist at the Institute of Advanced Studies, that because so many really transcendent minds in mathematics all came from the same small area of Prague, they must have had a shared Martian ancestor.)