Thanks for posting! As you have seen, the Records > Sort menu does not include an option to specify found sets. Instead, you might want to perform a search or 'Find' (select the magnifying glass icon or View > Find Mode) for the particular grade that you want to view prior to sorting.
Alternatively, you can try adding a button on your layout that would perform a script to automate this for you. Here's one way to do so:
1. Go to Scripts > Scriptmaker > New
2. Choose the 'Enter Find Mode' script step. Keep the 'Pause' option checked, and the 'Specify find requests' option un-checked
3. Choose the 'Sort Records' script step. Check the 'Perform without dialog' option and check the 'Specify sort order' option. Choose your 'grade' field and how you want the 'grade' field to be sorted.
Your script will now look like this:
Enter Find Mode [Pause]
Sort Records [Restore; No dialog]
Save your script and add it to a button. Now when you click on the button, you will enter Find Mode, you will enter the grade value that you want to print, FileMaker will find that specific grade and then sort the records accordingly.
Hopefully this helps or at least gets you in the right direction. Let me know if you need further clarification.