Daughter not invited to party/s. What do I say to her?

[SchoolMum66]

My 7 year old daughter is very upset as she was the only girl in her class not invited to a party. This is not the first time for both my daughters. My daughters are pretty 'normal'. The older sister, 9, does have mild social awkwarness issues, so this might be expected (though not nice). But my 7 yr old is very good socially, kind, friendly, plays easily with everyone. Our school parent body does suffer from terrible 'cliquiness' (is that a word??) with lots of social climbers/try hards. I am not in the 'clique' so expect a certain amount of snobbery and have to be thick skinned (that's life). But this is not fair on my daughters! And very crushing for them. So my question is...there are only so many times you can say "Oh there were probably limited spaces etc" (which isn't nice anyway as not nice to be the one who is left out). Any other suggestions of what to say to my daughters? I don't want their self esteem completely crushed :(

In response to some wondering...my daughter gets on fine socially at school. In parent/teacher meetings I have always been told how well she gets on with the other children and is popular. And this is what me and my husband observe also. So no problems there I don't think.
She isn't always excluded from parties, just a few times. But it is obviously very hurtful.
When I say there is a cliquey parent group, there is no tension between parents, just some of us don't 'make the grade' as we are not rich enough or cool enough! But so cruel that the children must suffer. I agree on other's thoughts about small schools.
Anyway the party was on last Friday after school (when I posted) and I didn't make a big deal of it. Was good to get some helpful advice. I have ignored the mean comments from one particular poster who obviously has issues.
And I tried to give my sweet (though sad/crushed) 7 year old a lovely weekend. We went camping. And it rained! :)

And the party was after school on the day I posted this, and my daughter stood there watching the party girls and invitees all excitedly leave school together to go to the party! |Heartbreaking.

I'd move her to a bigger school if you can. I think the second half of primary having best friends etc is important and class dynamics can get very set. She sounds lovely and you don't want this to affect her confidence. I think small schools seem sweet when they are tiny but their needs change as they go through primary.