So I was quite lazy in my year of GCSEs and under the misguided impression that they did not matter when applying for US uni's. So to put simply I did not obtain the best results, a few A's A* and 2 Bs and a C. Anyway, If do have a prediction of all A*s for A level sciences and maths, and have a 35/36 on the ACTs plus all the extra curricular activities, will my GCSEs still hugely penalise me when applying to Stanford and other universities, despite explaining how i was not mature then and did not fully understand the significance of exams?