Was wondering if anyone out there has a lot of experience with the US high school system? We have been offered the opportunity to relocate to the US and have a DD currently in a selective indie. She would be able to attend either a private High school or a local state school if we get a place (given out by lottery as it is one of the top 10 US High Schools).
Our DD is quite far ahead academically and is relishing the opportunity to take different classes, not fixed by year group. The private school is offering us a completely tailored schedule as long as the core subjects are covered as well as the prospect of DD graduating early if she wants to do so.

I have no first hand experience of the US system but expect it to be quite a culture shock for DD going from a highly selective all girls environment to a US High School.

Is there anything we need to be particularly weary of (apart from BOYS )?

I have several nieces and nephews educated in the public (state) system in the US. However I think different states are quite different and schools can differ even within a state.
You're welcome to PM me and I'll answer if I can but not sure if it will be very relevant.
One of my nieces started her education in the UK (a close friend also went to the states for a couple of years in her teens). Both find that they were academically significantly ahead of their peer group.

I lived in the states for six years and found their education system to be behind the UK.

I spent a lot of time with the local children in our community*I took the girl next door on our take your daughters to work day and they always invited me to Thanksgiving and even took me to hospital once) and found them to be nowhere near the levels of my nephews of the same age back home.

I lived in Seattle and you had to live in your school district. If you moved you had to leave the school. Their system would certainly sort out the cheaters who pretend to live in a house close to the school but don't really.

We lived in the "boonies" as they called it but the school bus called at every individual property and absolutely no families drove their children to school. That kept a lot of traffic off the roads and helped the children to get to know each other.

How long will you be there? I am sure she will have a great time but if she has a chance to sit an exam and perhaps go into the year above it would be a good thing to consider. DG

Thanks for your replies.
We are going to be either sending her to a slightly selective private school or a local charter school which happens to be in the top 10 in the US and top in California (places are given out purely based on a lottery). We are moving her up a year group and she will have the opportunity to take at least 5 AP exams during her 4 years of High School (a requirement for both schools). I think APs are like an AS level but am unsure. She can also take classes at her local community college and get credit from her high school if the class is not offered by her school.
We will be there potentially for the rest of her schooling, but we can flex that if necessary. She hasn’t decided yet where she wants to go to university (it’s early days!).
It seems that the system is more flexible but I am still worried that we are taking her out of a very good school here as I had also heard the American system was behind..

My understanding is that the system is indeed much more flexible so potentially could suit her well.

My thoughts would be that if you have the options you describe ( and are not dependent on a huge inner city state school for example) then it's not likely to be disastrous and you should consider her education in a broader sense.
The system is definitely different with an emphasis on different aspects so trying to replicate what you have now might lead to disappointment.
There will be a lot of cultural adjustments to be made for the whole family so not being under too much pressure academically right from the get go might not be a bad thing.
Making the most of new experiences and opportunities will also help your DD post 'A' level.

I know many families in a similar situation where the youngsters have come back to the UK for University. In the past the costs were given as a factor but I don't know if this is still the case. The other factors were requirement to take a broad range of courses in the US ( which may be am advantage for some) and length of courses.

I was talking to my oldest niece last night (has moved to the UK post degree). Her feeling (and this is very much supported by her youngest sibling - and this is still very subjective and based on their state - not California) is that their schools offered a good education in science, maths, art, "English" but their education in history, geography, politics was woeful. The youngest sibling just left school and came to visit last summer and happened to be with us for our school's open day. His response was to marvel at the humanities (at his school he says history was taught entirely by PE teachers who read from a book) and to reflect on the fact that here he'd probably have done Humanities A levels whereas he's doing a building/construction degree in the States.
But different states are different and your dd is also older so probably already has awareness of what interests her.