I seriously doubt that is the reason - on the contrary, I constantly hear that people would like more male teachers. However, I don't think the salary is sufficient to feed a family. Not sure if that is the main reason, but it might be a factor in men's decisions.
I went to get a elementary teacher degree. I dropped out after a year and a hald. Between being the only guy in a class of girls (it isn't as much fun as it looks) and having to put up with their sh (you think men are bad about dick jokes? try being around only women for the entire day) there is also discrimination from teachers (i had to prove myself every time, and was assumed to be riding on the work of the rest of my group on group assignments), parents were also quite suspicious of me. Though, the kids were great and didn't give a rats ass if I had a penis or a vagina.
I don't think that is as much of a problem here in Germany, so I doubt it is the major deterrent. Though in general being a teacher seems rather risky to me. Certainly if pupils or parents want to screw up your life, they have all the possibilities to do so.
Ah, my comment was only meant to include North America; I am not at all sure whether elementary education in other places has equal amounts of gender-iniquity.
I have heard the same complaint about almost all teachers being women here in Germany (at elementary school level). And of course we worry about paedophiles, I just don't think it has reached witch hunt proportions yet.
