Assertiveness

[IcelandicWarriors]

How do you encourage assertive behaviour in a 6 year old / yr 1?

DD appears to be dominated by her best friend and often comes home saying she has been called a baby, stupid, doing things wrong, last best etc.

She is even upset about a 4 year old from reception who appears to dominate her too.

DD is very sensitive and doesn't understand this type of behaviour.

Social stories can be good - google them.
Talk through situations with her and rather than criticising (I'm sure you don't - but it is easy to do) e.g. Why didn't you stand up for yourself? Talk through things she could say in the future, practice with her etc.
Catch her teacher at a quiet moment and ask for her help. I did this and DDs teacher looked out for moments she was being walked all over and would back up DD to help her feel confident and supported. She'd interrupt with strategies e.g. X is wonderful at art, I'm sad to hear you being so upset. X could you politely tell Y that you don't like her speaking to you that way.
Generally build her confidence and awareness that it is good to stand up for yourself. Praise a lot if you ever hear her standing up for herself with siblings.

I will have a look thank you. Will the teacher think I'm being picky if I speak to her about this?

Her siblings at in their 20s. I worried she is going to become a target because of her nature.

Is she assertive at home? Is she allowed to make decisions and say no/explain why she does or doesn't want to do things? I'd try and build up her skills at home, but have discussions about respect. Even at a young age you don't have to stand for name calling and if it was my son I'd have conversations about how friends should make you feel good and not say unkind things to you. She can pick a new best friend! Or have her friend over for a playdate and see how they interact/get to know her parents. If my son was calling friends, or anyone else stupid I'd want to know.