CC Ādi 15.5
śravaṇa-mātre kaṇṭhe kaila sūtra-vṛtti-gaṇa
When the Lord was studying grammar at the place of Gaṅgādāsa Paṇḍita, He would immediately learn grammatical rules and definitions by heart simply by hearing them once.
Śrīla Bhaktivinoda Ṭhākura says that the Lord was given lessons by a teacher named Viṣṇu and another teacher named Sudarśana. Later on, when He was a little grown up, He was under the care of Gaṅgādāsa Paṇḍita, who taught Him grammar of a higher standard. Anyone serious about studying the Sanskrit language should first learn grammar. It is said that simply to finish studying Sanskrit grammar takes at least twelve years, but once one learns the grammatical rules and regulations very nicely, all other scriptures or subject matters in Sanskrit are extremely easy to understand, for Sanskrit grammar is the gateway to education.