I posted a while back in another Topic about my 9 year old becoming moody, unco-operative etc and didn’t receive many helpful responses - most were along the lines of ‘my child’s nothing like that’.
But I then found lots of old threads, posters who were having a similar experience to me (and you OP).
You’re definitely not alone. There is a shift in behaviour and we are seeing physical changes in dd that suggest hormones are kicking in.
We are trying to ensure consistent boundaries, patience but not tolerating rude, unkind etc behaviour.
We are also trying to offer dd more independence gradually, if she can demonstrate she can be responsible.
Eg she can walk to school alone if she can show she can get herself ready for school on time independently, without us nagging her to hurry up every two mins.
If there are activities she wants to do then she needs to help with prep - eg making the picnic for a day out or prepping/tidying when baking etc. An activity that involves a sugary treat needs some physical activity too (eg a long walk for ice cream).
We try to include her in deciding what to do on holidays/weekends (to the extent practical). Eg on holiday we each chose two activities we wanted to do then all agreed we would do all the activities with a smile and without sulking.
Screen time is the big carrot and we try to keep it back until after dinner, as a reward for good behaviour. We also insist on some physical activity.
We’ve really noticed dd needs much more sleep, she is never up before us. This makes term time often the hardest as she is tired and grumpy. We don’t arrange things for any earlier than 11-12pm at the weekend and let her sleep in as late as she wants.