A Taliban leader, Khalifa Umar Mansoor, made the claim in a phone call to The Associated Press from an undisclosed location.
Mansoor was the mastermind mind the December 2014 attack on an army-run school that killed over 150 people, 144 of them children.
Mansoor says his four-man team conducted the assault at the campus in the town of Chasadda. He says it was in revenge for the scores of militants the Pakistani security forces have killed in recent months.
The main spokesman for the Pakistani Taliban, Mohammad Khurasani, also reiterated the claim of responsibility.
Taliban attack Afghan forces in country’s north, killing 14