This depends on how your English standard is. However, if your English standard is not that good, then the earlier you go to school in the US, the better. If your English is good, then G10 is ok. You can spend the time getting used to the curriculum and the way of teaching in the first year, then you start to run afterwards. But if the English standard is not good, you cannot even talk and so the more time that you have the better.。