There are more advanced options (using bcdedit or bootrec) which will do what the Fix Boot option does, but can restore the BCD itself. The repair tool can only fix the BCD (to my knowledge, this means that it can only fix entries that are incorrect and etc). However, if the BCD is corrupt, then it has to be replaced, which the Repair Tool cannot do. You have to be inside a Command Prompt to do anything like that (which bcdedit and bootrec are command line tools).
This is just for your future knowledge, but
this tutorial could save your kid a few days of not having a computer. Also, the WinRE (Windows Recovery Environment, which is what you were using, most likely) is the same between Windows 8 and Windows 8.1. They haven't updated it (at least to my knowledge).