I think we would keep the top 5% scores, and the remaining 5% would be filled with the people able to "affect the randomness" (read bribe) the best. There is a

I think we would keep the top 5% scores, and the remaining 5% would be filled with the people able to "affect the randomness" (read bribe) the best. There is already a degree of randomness inherent, since for example students don't all study all the material with exactly the same level of attention to each individual part of material. And some will be tired the day of the exams. Some will have something else on their mind while studying due to their relative being in the hospital. Some will by chance happen to guess right on some difficult task. etc. So you already have randomness.