Are they weighted less than, say, GCSE results or standardized test scores? Or does it depend on the reputation of the applicant’s high school (to the extent US colleges are familiar with different schools in the UK)?
FYI - for those who are not familiar with the UK educational system, the transcripts of UK students typically show only GCSE and A level results. Since A level exams are not taken until the end of Year 13 (equivalent to US 12th grade), secondary schools issue “predicted grades” that students list on their university applications.