A student at our school has found a bit of a "hack" into the muted grade lock down that I would like the share with the community. The student discovered the hack, told us about it, and even made a YouTube video showing the exploit.
The way it works:
A student viewing his/her grades can input predictions about their grades to fudge with the numbers. This even works when a grade is muted. So if a 100 point test has yet to be graded, then a students can "guess" they will receive a 90 and see how this score will effect their overall grade.
Our student discovered that when guessing grades an arrow will appear allowing the student to revert his grade back to the original value. However, if the student guesses his/her grade correctly, then the arrow does not show up. Essentially telling the student that his guess was correct.
See video: https://youtu.be/ftSN2LjEa3U