Make the gradebook able to collapse any column, not just through specific filters. K-12 teachers just want to be able to collapse whatever column they want instead of having to scroll through all of the grades. The filtering is a start, but teachers just want to collapse any column at any time.
The collapse feature should also allow the columns to be collapsed forever until the user un-clicks it. This should not be something that a user should have to click every time the gradebook is opened.