Question: which student had highest grade | Here are the first and last names of the student who had the highest grade. | which letter grade has the lowest grade point?
SQL: SELECT DISTINCT T2.lettergrade FROM ENROLLED_IN AS T1 JOIN GRADECONVERSION AS T2 JOIN STUDENT AS T3 ON T1.Grade   =   T2.lettergrade AND T1.StuID   =   T3.StuID order by T2.gradepoint limit 1