University performance is normally much more relevant than high school grades once you are recruiting from college. High school results may still appear on an application in some markets, but they are usually only one small part of a much newer academic and professional record.
If your university GPA is strong, you have relevant experience, and the rest of your application is competitive, an imperfect high school transcript is unlikely to be the defining factor. Conversely, excellent high school grades will not rescue a weak recent profile by themselves.
The broader principle is that firms look for a consistent signal of academic ability and achievement. This overview of GPA expectations in consulting recruiting is a better benchmark for where to focus your attention now.