What defines the quality of a education one can attain in a certain educational establishment?

Average GPA helps. The minimum GPA and test scores also shows the level at which they teach. You should look for a college with a big program in the area you want to pursue. Class sizes might also be a personal factor; do you like having individual attention or are you okay with more lectured based teaching? If you are in the US collegeboard.org is a good site for searching schools, they even have quizzes to narrow down the search.