College football rankings, grades: Defense leads Clemson to 'A-', Tennessee earns 'F' in Week 12 report card | CBS Sports Headlines College football rankings, grades: Defense leads Clemson to 'A-', Tennessee earns 'F' in Week 12 report card It’s time to grade the College Football Playoff contenders that shined and … Continue reading College football rankings, grades: Defense leads Clemson to 'A-', Tennessee earns 'F' in Week 12 report card