It's not localized to education, but a term that might work is collective/group narcissism, which WP says to be
a type of narcissism where an individual has an inflated self-love of his or her own ingroup
The terms collective narcissism and group narcissism appear to be equal in popularity, yielding about 500 hits each in Google Scholar. But these searches and an ngram search suggest collective narcissism is used slightly more.
Correct usage depends on the circumstances. For example, enmity between a group and only one other is not necessarily an instance of an "inflated view of one's ingroup" -- it may simply be disdain for someone else's -- but a new member adopting this enmity in order to feel part of the group arguably can be.
Note on first edit: My first edit mistakenly answered What is an antonym of "geek"? But, due to a sloppily written last sentence, it sounded like I was saying "people who use muggle to describe non-enthusiasts are geeks." My apologies to anyone who might have taken it this way; it was not my intention.