Despite the fact that the vast majority of children are online, our exploration of the user authentication literature and avail- able tools revealed few alternatives specifically for authenti- cating children. We create an authentication mechanism that reduces the password burden for children and adds customiz- able parental oversight to increase security. With Bluink, our industry partner, we iteratively designed and user tested three parent-child prototypes, with each iteration addressing issues raised in the previous iteration. Our final design is a parent- child authentication mechanism based on OpenID and FIDO U2F which allows children to log in to websites without re- quiring a password and enables parents using their mobile device to remotely determine whether a login request should be granted.