Find the kids that really play, and ask who taught them--you need to find a teacher than understands how a 14 year old thinks about music--As to guitars, acoustic guitar will actually yield better music faster--there are a lot more things to get under control when you play an electric--even still, 14 year olds have a high tolerance for uncontrolled noise, so it can work either way.

You can now get playable guitars for cheap at Target, and I suspect, if you check the newspapers, you can find them, or related ones used for even cheaper--Punkfolkrocker, you should re-post your list of good cheap instruments--