DD (6) not interested in socialising at school

[ReallyShouldBeDoingSomethingElse]

DD is in Year 1.

She plays interactively and happily 1-to-1 with particular friends on playdates.

At school, she chooses to spend her break times on her own, playing her own imagination games, wandering/running around etc. She seems genuinely content with this and is sometimes invited to join in with others but opts not to as she doesn't fancy the game they're playing.

At a party recently which she enjoyed an was fully involved in all the activities/games she didn't actually speak to or interact with another child once.

Should this be a cause for concern, or should I leave it be as she seems happy with this way of being?

Well speaking from experience I hated having friends forced on me as a child, I was quite happy with my own company, so I'd recommend leaving her be.

As long as she can socialise with others when needed then I don't think you need to worry, it will probably change as she gets further into primary school.

It's worth making sure she's being polite though when turning down offers in the playground.

I was like this as a child, so are my DSs esp DS1, I think as long as they are happy and content then it's fine. I miss that ability to immerse myself in my own imagination, try and let them enjoy it while it lasts.

@ReallyShouldBeDoingSomethingElse just let her be, some kids are just introvert. My daughter was the opposite, she had a group of friends in Reception who she interacted with on a daily basis,
but it was with adults she was reluctant but she had started talking to her class teacher, another Reception teacher made it into such a big deal saying she doesn't interact with "most" adults (there was only 1 class teacher who she had started talking to and one assistant so using "most" adults was incorrect when there are only 2 teachers as for every state school), so even if she came into contact with other teachers they were unknown to her. Knowing people from education sector, they thought it was weird for a teacher to pass comments like this.
My daughter answered direct questions from adults, yes she was reluctant in initiating with adults but with kids she was great. I took my daughter to a private school just to get away from this mad teacher and no problems with anything, like the way it was in her nursery.
I believe every kid has their own personality and it is important to give them time, not everyone is extrovert. If they are progressing well and your daughter's social skills is not limiting her to learn then it's fine, like the way it didn't limit my daughter's learning even if she is reluctant to talk to adults.