I have found that the biggest hurdle in teaching music is the notion that some people are "talented" and others are not, which of course is hogwash. Getting students past the self-consciousness of singing & playing an instrument is often the first step towards making real progress. Too many try to sing, or play, get frustrated that they don't sound the way that they think they should sound, and give up.
You see, when we pick up guitar for the first time, most of us already have in mind all of the great guitar players that we have heard, and are immediately comparing ourselves to them. This doesn't exist with ukulele...yet. There's many of us who know of the great modern ukulele players, but these players are not household names (at least in mainland USA), so I think students are more open to trying it out and not immediately convincing themselves that they have no talent than they are for guitar.
So is it easier than guitar? Sometimes...but then guitar is sometimes easier. (Try playing an E Major Chord on each!) Can it be a lot more accessible for students in the classroom than guitar? I believe so, especially at the Middle School level when the students are SO self-conscious and often afraid to try something new and fail.
I think it's time that we stop spreading the notion that the ukulele is an easy instrument. It's not. It is, however, more accessible to a lot of instruments, giving you as the classroom teacher a real chance to hook them before it's too late, and they've given up on music entirely.