Automate school class enrollment functions

Hello everyone. I work for a school that uses a custom and very robust learning management system. In this management system, we have to enroll students to specific classes using a CSV Import. Each class as a unique class code that might look like MATH6-1. That class code would be comprised of the MATH course with class section being the Grade-Section 6-1 (SUBJECTGRADE-SECTION is the format we use). So each student is assigned to a specific section number and all of their classes maintain that grade-section number combination (MATH6-1, SCI6-1, SS6-1, ELA6-1). The issue is that it takes us a really long time to manually build the file that matches the student number with each of the class codes. See the attached file for an example of what the enrollments CSV look like.

In our master student export, we have access the StudentNumber, Grade, and Section numbers. Is there a way to use the master student export to automatically create a row with the student number and class code for each subject?

Any help or ideas would be greatly appreciated. Thanks!