I'm going to be giving a friend's 10 year old son guitar lessons tonight, but I'm not exactly sure what I should be trying to teach him. It's not his first crack at guitar, he was given lessons by an older gentleman more into rock n' roll and older guitar styles that I'm assuming didn't catch on with him.

He wants to be able to play guitar for concert band class (unlikely, imo) and jazz band, and just be able to walk in and know what he's doing.

I was thinking of trying to teach him basic chords (major, minor, 7th, minor 7th and major 7th), scales, and maybe basic chord construction?

I was looking for suggestions for songs for beginners. Personally, I only learned chords for the first couple weeks of my playing, and it wasn't fun, but it was a good foundation to build off of, imo.

Please suggest anything else you guys think would be good to learn for a beginner. Thanks.
This post may contain my opinion and/or inaccurate information.

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Find out what he does know 1st. Pick a song and show him all the chords/note in that song. Then put them together in the order of that song. Ask him what songs he would like to learn.
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Ask him to get the lead sheets for the songs in his school's jazz band class and go over those with him.
Another person taking a job they are ill-prepared for. Third one in as many days...

I'll say this: whatever you do make it fun. Unless the kid is already extremely driven he'll need something interesting to keep his attention so spend some time finding out what he likes and see if you can link that to music somehow: theme from his favourite TV show or video game, suitable versions of music he already listens to, that kind of thing.

Whatever it is, just don't make it dry and dull unless you can tell that this is what the sprog wants.
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“A man who mistakes secrets for knowledge is like a man who, seeking light, hugs a candle so closely that he smothers it and burns his hand.”

+1 on making it fun. Regarding theory - I'd go practical first (teach him things to play), and then gradually filter the theory in over time. Theory is going to be boring unless there is something he actually gets to do to tie it to.
You could buy a guitar book for beginners and use that for ideas, injecting your own ideas along with it. The book I started on was great. I can't remember the name of it, but there were a few pages on how to hold the guitar, pick, place your thumb, etc, then it started out by teaching you the 12 bar blues, just using open E A and D power chords. Then it started introducing a few of the basic open position major and minor chords, then barre chords, and so on. By about halfway through, you were playing things like the opening riff of crazy train. You get the idea. As you went there would be little explanations about what you were doing, like explaining that a major chord was made up of a root, 3rd and 5th, and that you make it minor by flattening the 3rd. I felt like it worked well for me.
Good luck!