A family of Microsoft relational database management systems designed for ease of use.
Ok the first subform is the student listing, correct? That should only be:
SELECT tblStudents.CenterCode, tblStudents.StudentID, tblStudents.StudentName, tblStudents.StudentGender, tblStudents.DOB FROM tblStudents;
In fact, the Recordsource need only be tblStudents.
The Second subform is where the grades should be and that should be just tblStudentProgress. No need for a SQL statement. I said before that the filtering by Centercode is a function of the link between the Main form and subform, nothing else.
But this is not what I asked for. I told you to create a query that includes tblStudentProgress and tblCourse. Filter that query for a specific CenterCode. That query should return a record for each student for each course. So if there are 4 courses, then there should be 4 records per student.