Kṛṣṇa's receiving education from Sāndīpani Muni is described by Śrī Nārada Muni as follows: "In the beginning, Lord Brahmā and others are like clouds of evaporated water from the great ocean of Kṛṣṇa. In other words, Brahmā first received the Vedic education from Kṛṣṇa, as the clouds receive water from the ocean. That Vedic education or instruction which was spoken by Brahmā to the world was then reposed upon the mountain of Sāndīpani Muni. Sāndīpani Muni's instructions to Kṛṣṇa are like a reservoir of water on the mountain, which flows as a river and goes again to mix with the source, the ocean of Kṛṣṇa." To be more clear, the idea is that Kṛṣṇa actually cannot be instructed by anyone, just as the ocean does not receive water from any source but itself. It only appears that the rivers are pouring water into the ocean. So it is clear that Brahmā received his education from Kṛṣṇa, and from Brahmā, via the disciplic succession, this Vedic instruction was distributed. Sāndīpani Muni is likened to the river which is flowing down again to that same original ocean of Kṛṣṇa.
The Siddhas, the inhabitants of Siddhaloka (where all are born with fully developed mystic powers), and the Cāraṇas, the inhabitants of a similar planet, pray to Kṛṣṇa as follows: "My Lord Govinda, the goddess of learning is decorated with fourteen kinds of educational ornaments, her intelligence is all-pervading within the four departments of the Vedas, her attention is always on the lawbooks given by great sages like Manu, and she is appareled in six kinds of expert knowledge—namely Vedic evidence, grammar, astrology, rhetoric, vocabulary and logic. Her constant friends are the supplements of the Vedas, the Purāṇas, and she is decorated with the final conclusion of all education. And now she has acquired an opportunity to sit with You as a class friend in school, and she is now engaged in Your service."
Kṛṣṇa, the Supreme Personality of Godhead, does not require any education, but He gives a chance to the goddess of learning to serve Him. Being self-sufficient, Kṛṣṇa does not require the service of any living entity, although He has many devotees. It is because Kṛṣṇa is so kind and merciful that He gives everyone the opportunity to serve Him, as though He required the service of His devotees.