And while GPA has considerable relevance as a measure of college success, it doesn't tell the whole story and for some purposes, it misses the mark entirely. George had a 4.0 in high school, spent his college years drinking and goofing off and still got a 3.5 in college then went into the family firm. Herman had a 2.5 in high school, worked diligently to get a 2.5 in college, was stimulated to new insights, and emerged from college with new aspirations and skills he had never contemplated. The answer depends on your purpose in defining successful. Another ingredient in the GPA potpourri is the student's approach to influencing grades independently of achievement.
Some students concentrate on learning without regard to grades.
Others concentrate on the instructor's grading style and on past tests. But often supervisors' ratings are the best criterion you can get and sometimes they are excellent. Ratings based on a job analysis covering specific instances and using trained raters occasionally work really well. And occasionally with one supervisor, who is intimately familiar with a large group of workers, you can just ask who's good and who isn't and get a meaningful ranking. Knowing which workers are the most proficient or the most productive may not be the criterion you need.