By sorting the records for one student--either in a found set or in a sorted portal, you can use a script to go to the last record or portal row and move up from there to capture the values of each "lowest score" that you want.
WIth a sorted relationship sorting scores in ascending order, List ( RelatedTable::Score ) would list those lowest scores at the beginning of the list and you could use something like the LeftValues function to extract the N lowets scores. (If your sort in Descending order, the RightValues function can be used.)
And ExecuteSQL() could be used to extract a list of N Lowests scores as well, but without the need for establishing a relationship for the purpose.
That's brilliant. And if I use a portal I can also solve the next problem--which is I have to know how many possible points need to be subtracted from the total as well. Thanks Phil. I'll try to write the script.