First, office suite applications are not computer science. If you want to teach the CS version of word processing, teach them LaTeX. In the meantime, I recommend something that I didn't do: start with a functional language like Scheme (I started with K&R). I TA'd for a Java intro class and it never went well. All the PL (programming language) grad students I know hate C++, and that leaves Python, Ruby, and the functional languages.
Scheme is pretty simple, and probably appropriate for HS-level coursework. One of my intro classes was with Scheme and I liked it (we used the wizard book, a friend of mine had The Little Schemer at his school). I've heard good arguments for using functional languages for introductory courses, but I don't really remember them
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