Most people seem to think of age as a natural demographic by which to separate people
I sense this. I am still in my 20's and look very young. My DD goes to a magnet school which requires parents to apply 8 months before K. Young parents, like me, are less likely to plan ahead for education, so most if not all of the parents in my DD's grade are older than me & many signifianly so.
The first year there was hard for me, because I think I made some of the other mom's uncomfortable. They would unintentionally click together during activities so I had to invite myself over, which I did.
Things are better now, because we have been together for 2 years.
But every once in a while, I still feel like the young, imature, broke, mother as they drive off in their BMWs.
And I also imagine that every once a while I make them feel old or over weight just by being there.
Which is one of the reasons why I like it here. We are equals
