'what do SAHMs do during the day when their DCs are at school?'
I do whatever I want. Usually abit of study (I am doing an OU degree), helping in school about once a week, seeing elderly relatives, shopping, housework, watch telly, see friends, go out with hubby (he works shifts so is around in the day alot). I am actually very busy usually. I love the sense of freedom though that I can meet my childs needs at the drop of a hat; eg if they are ill at school etc, rather than have to worry about childcare or some companies needs and lining someones fat pocket. Also we can relax if DH has to work late or overtime as I am always here to look after them.
I am quite proud that I am doing what I want even if society looks down on what I choose to do. (although it took me a while to adjust after being a WOHM) I would rather have my time for me/my family than sell it to an employer. Also, we can manage on one wage which is a good position to be on as if need be I could get a job should DH be unable to work. If we relied on both wages and he became unable to work we would be in a worse state. Getting a second job would mean more outgoings like a 2nd car, work expenses etc and dependency on a 2nd employer (scary in this economic climate).
The people who make snide comments to me are usually WOH mums or people without kids. Doesn't bother me, whats the most they can say/think; I am dependent, old fashioned, lazy, stupid etc etc none of those offend me TBH as I am really appy with my choice.
I don't see myself as especially dependant as DH depends on me just as much to enable him to do his job. Most WOHMs rely on both wages to pay the mortgage etc so would be just as screwed if their DH cleared off. Anyway, if you study/volunteer etc like many SAHMs do, you should be able to get a job if need be, no point worrying about that all the time though, just enjoy the time with your kids.