Hi Kay! You should be able to accomplish this by setting up your bar graph as follows (assuming you have columns named Student, Grade Level, Score, Subject as columns in your source).
Dimension: Score
Metric: Record Count OR Count Distinct Student
If you wanted to add Grade or Subject as a Breakdown Dimension in your chart, you could do that as well, and make it a stacked bar, or not.
Sort by Score Ascending
You can then add filter controls for subject, grade, etc. You will probably want the subject filter to be single-select, unless you opted for Subject to be your Breakdown Dimension.
Hope that helps!
Laura