Sadly, I get this question a lot—and, even more in the Covid education world. Grades can often not be trusted as an indicator of progress or performance. There are multiple reasons for this when it occurs. Grade escalation is a real phenomenon. In other words, grades do not always indicate mastery. Homework is often done online with the students able to do and submit the homework multiple times. This approach often does not lead to mastery and often does lead to lack of retention. Learning is often not occurring.
The short answer is that it is exceedingly difficult to get students to strive for mastery if it is not required as part of the curriculum. I have worked with students who are willing to do what it takes. One approach is to get a hard copy math book as most schools do not have such books. Then, the student needs to basically self-teach themselves from the book. There are generally good lessons in books with lots of problems to practice. I work with students consistently where I implement this approach. Let’s talk more about this.
I do want to emphasize that this is a situation when my connection with students is critical. A lot of trust is required for students to change the path they are on.