When grades are entered in the Gradebook and the "Enter" key is pushed, the grades are saved and more entries can't be made until "Edit Grades" is selected again. The only way (I think) to move in the gradebook to the next student is to use the arrow keys or mouse.
When entering grades in the gradebook for a large class it is more efficient to use a number pad to enter to the grade. But you loose that advantage since the "Enter" key does not move to the next student to enter their grade but stops the grade entry entirely. Spreadsheets work by moving down a row with the "Enter" key to efficiently enter data.