UK to US School transition for teens

Hello

My family and I have recently moved to Virginia from the UK. We have been here around 3 months and plan to stay for 3 -4 years. I have 2 children aged 15 years (currently in US 10th grade) and a 17 year old in 11th grade.

Just wondering if any other Brits can offer any experience/advice/reassurance regarding teenagers transitioning into the US education system from the UK?

To say it's been rocky over the past few months is an understatement! My son wants to move back and is already considering options back in the UK and my daughter is incredibly worried about failing High School as it is so different and she feels like she is failing in every subject. Curriculum and teaching methods are very different to the UK. She is constantly stressing over not getting good enough grades and failing to get into College. She keeps on telling me that every grade in 10th grade matters and will affect her final diploma score. She says that her teachers are commenting on her grades. Back in the UK she was on course to get good GCSE exam grades next summer but this is now not an option due to our move.

Obviously, it is early days for us as we have not been here that long but it would be lovely to hear from anyone that can tell me it gets better or anyone that can share experiences of UK teenagers getting on ok.

Sorry for the rambling message and thank you to anyone that can help.