Why do they need to speak perfect English? Are you worried the child will develop an accent or something? Unless the child is spending 24 hours a day with this

Why do they need to speak perfect English? Are you worried the child will develop an accent or something? Unless the child is spending 24 hours a day with this person for months I don't think that's going to happen. And what "cultural habits" are you worried the child is going to pick up or not pick up from spending time with an immigrant?