So this is the advice we give to teachers when setting up Assignment Groups:

If you have an assignment group with a graded assignment in a quarter, than when the quarter closes, the weighting of that assignment group will be locked. What this means is that if your assignment groups look like this:

- Homework 20%
- Quizzes 20%
- Tests 30%
- Projects 30%
and you have at least one assignment in each of those categories, then when Quarter 1 ends, those grade weights are set in stone for the rest of the year.

To avoid this issue, and to permit you to tweak your category weights at the quarter or semester, we recommend you set up a group for each category in each quarter. So:

- Q1 Homework 20%
- Q1 Quizzes 20%
- Q1 Tests 30%
- Q1 Projects 30%
- Q2 Homework 20%
- Q2 Quizzes 20%
- Q2 Tests 30%
- Q2 Projects 30%

- Q3 Homework 20%
- Q3 Quizzes 20%
- Q3 Tests 30%
- Q3 Projects 30%
- Q4 Homework 20%
- Q4 Quizzes 20%
- Q4 Tests 30%
- Q4 Projects 30%
Canvas will automatically scale the total percentage, so the fact that the total comes to 400% will still lead to the desired grade calculations.

I understand why Assignment Group weights would need to be locked when a grading period is closed, but it seems like at the close of the grading period, Canvas could prompt the teacher to copy over the previous weights into the new grading period (or change them if that teacher wished) and then only make visible the assignment groups relevant to that current quarter, so that a teacher doesn't need 20 different assignment groups by the end of the year if they want to maintain the flexibility to make changes next the next quarter.

Scott Cunningham, you might be interested in this related feature idea: