A higher education college suffered “a significant malicious cyber attack” meaning students could not access their GCSE and other exam results online.
Myerscough College, in Billsborrow, Lancashire, said it meant staff had to email each student individually with their grades.
Online enrolment was also affected following the attack on Thursday.
A spokesman said there had been no breach of student data, and Lancashire Police were investigating.
In a statement the college said it had been “among the most challenging days in college history”.
It said the “denial of service” attack “severely damaged all IT infastructure” and systems were still offline so staff could only be contacted through social media.
“When it became apparent that the server wouldn’t be back online, we decided to manually email all students their grades,” it said.
“As many hundreds of students were affected, this has taken a massive effort from staff through the day, who have worked quickly to try to contact everybody.”
“We apologise to any student impacted.”
Myerscough College is a specialist college and university centre offering courses in sports, equine studies and agriculture.