Yes, exam marking would be a good earner for the end of summer term, especially as there's less supply work during those last few weeks. I applied for GCSE exam marking this year (with the exam board that famously got their admin staff to mark RE papers), but got rejected. They said that as a NQT on supply, I have insufficient experience with teaching and assessment and they expect a current employer's reference from a school, not an agency. So why do they advertise for PGCE students to mark papers? And a few weeks ago, they were advertising for "specialist graduate markers" with no teaching qualifications at all. In my subject, too. ThereI've seen adverts for exam invigilators over the summer term, so that's another possibility?