Vaishnava Samhita. Shri Vallabhacharya Charitam I. Vol III Book VII Chp 1 Shlokas 25 - 26

अष्टमे वयसि प्राप्ते द्विजत्वं प्राप्य वल्लभः  |
पपाठ वेदं वेदान्तं वेदाड्गञ्च महाप्रभुः  ||
पिता लक्ष्मणभत्तस्तु श्रीकृष्णचरणं स्मरन् | 
पावने जाह्नवीतीरे संप्राप परमां गतिम्  ||

The ritual of Upanayanam was performed when he was eight years old. From that time, he started studying the Vedas and other Shastras. Lakshmana Bhatta left for the divine abode, engaged in meditation on the lotus feet of Lord Krishna on the bank of the pious Ganga.