@rjpollard  

Within an assignment group, weights are determined by points. You could make them 40 and 25 to accomplish this. I do this with my exams where some are worth 10, 15, or 20 percent of the grade -- I just make the assignment worth that many points.

This is sometimes difficult to make happen with Classic Quizzes where the points are determined by the questions inside the quiz. In this case, you can split your assignment groups into two and make them worth 40% and 25% respectively. Note that this will not work if you drop any of the assignments in the assessment group.

The grade will never quite give an accurate representation with a weighted gradebook until all of the grades are in. What I mean by that is that once your 40% assessment comes in, it is the only assignment in that group so it will count towards 65% of the grade. Students who do poorly will be freaking out. When the other assignment is entered, then it goes back to the 40% and 25% that you wanted and the students freaking may be reduced. If you split the assignment group up into two parts, then you only have 75% of the grades in until that 25% assessment is entered, so it scales the points up, but it does it across the board rather than weighting that one assessment worth 65% of the grade.