The main duty of the teachers was to inquire who those Vaisnavas were that came to teach Prahlada and spoil his intelligence

Expressions researched:
"The main duty of the teachers was to inquire who those Vaiṣṇavas were that came to teach Prahlāda and spoil his intelligence"

Srimad-Bhagavatam

SB Canto 7

It was surprising, of course, that in the same school the other boys of the Daityas were not polluted; only Prahlāda Mahārāja was supposedly polluted by the instructions of the Vaiṣṇavas. The main duty of the teachers was to inquire who those Vaiṣṇavas were that came to teach Prahlāda and spoil his intelligence.

SB 7.5.9, Translation and Purport

Dear son Prahlāda, all peace and good fortune unto you. Kindly do not speak lies; just reply with the truth. These boys you see are not like you, for they do not speak in a deviant way. How have you learned these instructions? How has your intelligence been spoiled in this way?

Prahlāda Mahārāja was still a boy, and therefore his teachers thought that if they pacified the little boy he would immediately speak the truth, revealing the secret of how the Vaiṣṇavas came there to teach him lessons in devotional service. It was surprising, of course, that in the same school the other boys of the Daityas were not polluted; only Prahlāda Mahārāja was supposedly polluted by the instructions of the Vaiṣṇavas. The main duty of the teachers was to inquire who those Vaiṣṇavas were that came to teach Prahlāda and spoil his intelligence.