Hello @JenniferKolar. My first thought to answer your question is to set a grade policy for missing assignments, which can award a score of 0 for all Canvas assignments that are not submitted on time. That will ensure that students' grades are current. However, it does not look like there is a way to enforce this across an entire subaccount or Canvas instance, so the best option will be to require that instructors have that policy enabled.
But this does not entirely solve the problem you mention, as the current grade only reflects what has been graded at the moment. A student with 90% on 45 out of 50 points has another 855 points to earn if they want 90% in a class with 1000 points possible. The list on the /grades page only shows percentage, even if the class has points selected for the Total grade item. You could require that all assignments are scored 0 at the beginning of the term, but that can be so dispiriting. 😞
It looks like the best option is to hide totals in students' grade summaries, which prevents any score from appearing on the /grades page. Instructors can still see the total score on their view of the Grades page. Like the missing grades policy, it looks like there is not a way to enforce this option across an entire subaccount.