"I used to coach junior high basketball and every team I coached there was always at least one vocal parent who had concerns. Sometimes their perspectives were appreciated, sometimes they weren't. Sometimes they thought they were my assistant coach. And while I truly do value that kind of keen interest in their child's success, I do have to consider the class as a whole, just as I did the team, and the student in particular just as the player, and the entirety of the system as well. So I'd acknowledge how the parent felt and thank them for taking an active interest in their child's education. I would listen to their concerns, and assess possible solutions while reiterating that there's a standard curriculum for all the students and teachers to follow. If the solution was as simple as suggesting some expanded materials I might do that, but my concern would primarily be for the student, and to my profession. Trusting the process is my job. But no matter how realistic or unrealistic their concerns might be, I would do my best to maintain a dialogue, seeking to improve their trust in me and in the school."