Conversation so far:
When was Recep Tayyip Erdoğan born?
26 February 1954
Where was Recep Erdoğan born?
Erdoğan was born in the Kasımpaşa neighborhood in Istanbul.
Who were Recep Tayyip Erdoğan's parents?
His parents were Ahmet (1905–88) and Tenzile Erdoğan (née Mutlu; 1924–2011).
Who were Recep Tayyip Erdoğan's siblings?
Erdoğan had a brother Mustafa and sister Vesile. From his father's first marriage to Havuli Erdoğan, he had two half-brothers: Mehmet and Hasan.
Which school did Recep Tayyip Erdoğan's attend?
He studied Business Administration at Marmara University's Faculty of Economics and Administrative Sciences — although several Turkish sources dispute that he attended or graduated.
What did Recep Tayyip Erdoğan's do during high school?
In his youth, Erdoğan played semi-professional football at a local club.

Question: When did he graduate?
Self-contained rewrite: When did Recep Tayyip Erdoğan's graduate high school?