Not sure what you mean re qualifications, but I think it's illogical to give grades based on predicted performance. The whole point of issuing another grade is to see how well the student is doing at that time--to see how well they learned the new material, or at least to see how much they've improved or worsened. If you're just going to go by past performance, then just go by past performance explicitly, what's the point of using a made-up middle-man by predicting?