Random selection with conditional

hi guys am school teacher, and have a chess tournament , which needs addressing RANDOM duels between distitas schools, with 5 students per school, with the following conditions:
1. will not face each other or with schools from the same state .
2. enfrentarso between students will have the same average or the lowest difference , example: 8.85 juanito francisco vs 8.6

They can, please help me?
Thanks in advance. attachment