You can mark all students with a grade, a credit, Pass/Completed or Fail using the bulk update tool. This tool allows the user to assign a specific value such as a grade to every student in the class and then uncheck / change anyone it does not apply to.
First go to Class Detail and click on Grades/Credits. From there, you will click the link "Bulk Update Student Records..."
This will open the fields so you can mass assign one or more of the options to every student who is displayed. Be sure you review "View" status and only those students you want to affect are selected (e.g. Enrolled and Pending versus All).
Select a value and click Mark All. This will populate every student record with the selected value.
When you are done marking all students, adjust any student record that should not get this value.
Don't forget: Click Save