For any assignment that has .travis.yml file, Travis-CI.com will run automatically when the student accepts the assignment and after each push. The student repositories are all private.
When setting the assignment, if you give students ‘admin rights’ then Travis-CI will not run automatically. I believe this is a bug.
Yes, students can probably trigger travis themselves or I could write a script for it, but I am reporting it as a ‘bug’ to travis rather than finding yet-another-workaround for github classroom.
The discussions here are useful, but is there a better location to report a classroom bug?