Conversation so far:
where did Sarvepalli Radhakrishnan go to school?
Sarvepalli Radhakrishnan's primary education was at K.V High School at Thiruttani.
when did Sarvepalli Radhakrishnan start his academic career?
Sarvepalli Radhakrishnan started his academic career in April 1909 at the Madras Presidency College.
what was Sarvepalli Radhakrishnan's position there?
In April 1909, Sarvepalli Radhakrishnan was appointed to the Department of Philosophy at the Madras Presidency College.

Question: how long did he work there?
Self-contained rewrite: how long did Sarvepalli Radhakrishnan work at the Department of Philosophy at the Madras Presidency College?