Our grades and rankings are based on a variety of data. Each grade has a specific methodology - while these methodologies can include other grades as factors, they do not always overlap and as such, grades are not always affected by one another. The Overall Grade has its own specific methodology, rather than being an average of the other grades shown on your report card.
Because of this, it is possible to, for example, have an A Overall Grade without having any A topic grades or a C Overall Grade without having any C topic grades.
To review more on the grade methodologies, including factor sources and weights, check out: Where Niche Grades Come From. You can read more about how we calculate our rankings here: About Niche's K12 Rankings, About Niche's College Rankings, and more about where our data comes from here: Where Our Data Come From.