How simple are we talking? I'm currently teaching one kid how to play who was having a horrible time with basic open chords- D, Em, G, C, Am, etc. The real problem, of course, was i couldn't get him to practice. So, what I did was took this song that we were working on that used some of those chords, had him play through it, and asked him, "Now, what are the ones you seem to be having the most trouble with?" He was able to identify the changes, so i said, "Ok, now, how about we write a song that uses these chords, to help you practice? What one should we start from...? Ok, and what chord do you want to play next?" and went through it like that. Next week, he wasn't much better, but he'd decided he liked playing G-Em and back a lot, and could do those really well. so we did the same thing, played them together for a while, and then he went off to practice for the next week. At the end of that week, he wasn't much better, but was even more fluid at playing Em-G-Em, because he said they were "Fun."
moral of the story? Maybe 9 is too young to learn.
I think you see where I'm going, though... "write" a song with the pupil, or rather let them, that puts chords they're having trouble playing between together. They'll feel like they're creating something and will be excited enough about it to practice it (hopefully)... and even better, it saves you the trouble of finding an existing song.