You can update the applying to grade for one or many records in bulk via the Application Index.
First, then select the applicants(s) you wish to update. Note: all selected students must have the same grade level & school to change in bulk.
Once you've selected the applicants, click on Select Bulk Action --> Change Grade
Select the grade for these applications. You can choose to "send an email or text message notification to families" with the change. Finally, click "Change Grade"
Success! You will see a green banner notifying you that the change has been successful: