Well "ag" is short for "agriculture". Despite the name, most ag classes have nothing to do with agriculture; it's just that all vocational (welding, electrical, mechanical) classes are held in the ag building (a.k.a. the shop). Where I went to high school, you could graduate with a "completer" cord, meaning that you took a certain number of electives from a certain category (business, computer stuff, home ec). I took intro to ag (9th grade), ag business and marketing (10th grade), and ag structures (11th grade). If I graduated from that school, I would have gotten a completer's cord for ag.
Well, anyway, like I said before, Ag classes were for people who didn't want to take home ec (or "family and consumer sciences"), business (proper business, not ag business), or computer classes. So, ag classes were usually composed of a bunch of red-necks with horrible grades who and nothing to look forward to after graduating (Gah, my English skills are terrible, aren't they?). There were a few good, honest people in ag, but most of them were awful. Like I said before, there was this one girl in ag marketing who seriously spent all class period (we seriously did nothing in that class) talking about how she was allergic to her own vaginal fluids (and I really hope none of these people I talk about are reading this).
Now, you're probably wondering what I was doing in such classes (if you're not wondering, then f*ck you). Well, first of all, I really liked chickens and public speaking. Ag provided opportunities to compete in both poultry judging and public speaking. Secondly, I had very poor self esteem back then. I was convinced that I would be unable to get into college and that I would be a failure at life. There is one particular person responsible for instilling these thoughts in me, but I'd rather not get into that right now. So, there you have it.