The Treasure of Tavaros is great. It gives teachers the option (in game rules) to set a pass/fail %. It then judges Google Classroom assignments by pass/fail based on that % and gives points dependant on the score. Having this as a reward option on quest objectives would be far superior to the current reward system.
Currently, in student-paced mode, students submit an assignment and get an xp/gp reward without considering how they actually performed. This reinforces the "completionist" attitude of students who only wish to "get through" assignments to get xp.
If you add Treasure of Tavaros to quest objectives you could also use it to judge pass/fail based on % and automatically move students down a green "pass" path or a red x "fail" path. This would automate differentiation.