NC for this. I'm genuine!
When DS2 started school I made friends with another mum who had a child in the same class as ds2. All was well to begin with, we got on great.
As time went on she started to ask for things only small things, then moved on to asking me to buy her things when I went shopping and wouldn't pay me back claiming poverty without so much as a thank you.
She'd borrow things and I'd never get it back , she even sold something on Facebook that I lent to her.
She'd speak about others behind their backs to me and try and drag me into her relationship problems.
I finally clocked on (yes I admit I'm a bit slow! 
) and distanced myself. Was polite when I saw her but stopped inviting her over for coffee as I didn't want to be dragged into her drama or used anymore.
A few months passed and she randomly accused me of telling her now ex partner things about her and spying on her - her bare in mind I hadn't spoken to her other than a quick hello in months.
I told her quite brutally I didn't care about her private life and to stop dragging me into her dramas and assuming things.
Now the issue I have is that she works at ds2 school, and has been quite rude since this has happened.
She barges into me at the school without so much as a "sorry", she's decided to do a party for her child invited all the other kids in the class bar my son who is quite upset as they are very good friends.
She's taken things out of my sons lunchbox and refused to give them back (even though the policy is to leave it in the lunchbox until they go home!)
She's not watched my son properly on the playground and my son has been hurt by other kids even though she's meant to be supervising.
She's also told other parents things about me as they've told me. 
some of it not even true!
AIBU to think making friendships with school mums isn't worth it? And would I be unreasonable to change DS2 school? I feel very uncomfortable that someone like this is part of supervising my son at school hours or am I just being dramatic myself?