ほぼ正しく..結合を見てください。間違ったフィールドを参照しています
SELECT student.firstname,
student.lastname,
exam.name,
exam.date,
grade.grade
FROM grade
INNER JOIN student ON student.studentId = grade.fk_studentId
INNER JOIN exam ON exam.examId = grade.fk_examId
ORDER BY exam.date