CC Ādi 16.4

ei ta’ kaiśora-līlāra sūtra-anubandha
śiṣya-gaṇa paḍāite karilā ārambha
Word for word: 
ei ta’ — thus; kaiśora — the age of kaiśora (the age between the eleventh and fifteenth years); līlāra — of the pastimes; sūtra-anubandha — chronological synopsis; śiṣya-gaṇa — students; paḍāite — to teach; karilā — did; ārambha — begin.
Translation: 
At the age of eleven Śrī Caitanya Mahāprabhu began to teach students. This marks the beginning of His kaiśora age.