There is much good advice for job applicants on this site, but how about advice for the search committees? We wiki-ites have a unique perspective that might help search committees to not make dumb errors. I'll start…
Dear Search Committee,
Please understand that there is a fundamental difference between a job talk and a teaching demo. When you conflate the two, it may save you some time in the schedule, but it really messes up our presentations.
The job talk is aimed at adults, at faculty. I need to impress you with my research, and to do so I need to be able to explain my work fully. Undergraduates will not like this talk. They will think it boring and they won't understand some of the basic elements to the experimental design, the stats, or the broader literature.
The teaching demo is for the students. I can do a great teaching demo … you just need to tell me that you want this. I may even be able to dumb down my research so that it is palatable to undergraduates (although it will be a real stretch).
When I show up for the interview, don't spring on me, "Oh, we thought it would be good to invite our freshman-level class to your talk. You know, just to get their sense of your teaching style." I then have a roomful of bored students who will undoubtedly kill me in the review.
So, search committee members, just make it clear what is being asked for. And job applicants, you might want to be more careful than I was in my own expectations on the meaning of a 'job talk'.