See whether this year's applicants are better represented in the top category. If they were referred by a current top performer odds are that they are also. Referrals consistently rate as the highest quality applicants. Top performers seldom have great or even current resumes. People that are on the job market a long time have time to polish and improve their resumes.
Top performers come from many schools.
The best usually do excel at what ever school they went to. In a diverse world where many students are older or have to work, overall grades might not predict much. Grades in their major might show more. See if your current top performers had great grades first.