you are now using additional terminology - I take it subject is the course?
your basic query to determine the average per student would be
Code:
SELECT StudentID, Course, Avg(Grade) as AverageGrade
FROM Grades
GROUP BY StudentID, Course
save this query and call it say qryAvgGrades
then in a new query, modify the code provided by Paul to use this query
Code:
SELECT StudentID, Course, AverageGrade, LetterGrade
FROM qryAvgGrades LEFT JOIN LetterGrades ON qryAvgGrades.AverageGrade >= LetterGrades.lowerlimit AND qryAvgGrades.AverageGrade <= LetterGrades.upperlimit
Note you are using lookups in your table design. These will cause you problems - as you will discover in time. Better not to use them so you know exactly what your data looks like and how you need to construct your queries, forms and reports.