iphone passcode fails when trying to change child's Apple ID password

My son figured out how to change his iPad passcode and then promptly forgot what he changed it to, and his iPad is now in security lockout. I've tried erasing it, but it will not accept his Apple ID password. The little spinning thing pops up and never goes away. I tried changing his Apple ID password using my iPhone, which I've done in the past without issue. However, when I enter my phone's passcode as prompted, it just asks for it again. After asking four times, it says, "too many failed attempts." I know I am entering the correct passcode because I can use this passcode to unlock my phone.