Hi Sofia,
Thank you for reaching out in the Schoology Community!
Unfortunately, there is no way to "delete" attendance since blank cells are considered present in Schoology.
If you'd like to see Schoology add or change the way attendance is reported, please consider posting a Feature Idea in our forum to share your idea with other users and our Development Team.
Best,
Nina Lewis
Community Communications Specialist
Schoology | A PowerSchool Unified Classroom Product