Since they are current students, they do not need to go through the checklist or application process and you will want to delete their erroneous profile.

  1. Go to Core > User/Access > Profiles 
  2. Search for the student 
  3. Click the Profile for the Active Candidate
  4. Scroll Down to System Information 
  5. Click Remove User
  6. Click Delete
  7. Click Ok

Once you delete the duplicate profile, the duplicate application and checklist will also be removed.