Eton College has blocked access to Snapchat from its wireless network amid concerns over boys using it to send sexual pictures.
But the app, which allows people to send images which are then automatically deleted within seconds, can still be used by pupils using 3G connections on their smartphones.
Headmaster Tony Little told the Telegraph: "It is blocked from the Eton wireless internet system.
"Boys can still use it via the 3G phone network, but we hope that blocking it on our network will at least make them think twice.
"This is part of our continuing effort to educate boys in the sensible use of technology," he added.
Snapchat was hacked last week, with up to 4.6 million users' details leaked online.
The app has seen a huge leap in popularity in the past year, and was reportedly the subject of a failed £3billion takeover bid from Facebook.