[[__hector]]

Que tal algo asi:

Código SQL [-]
INSERT INTO Estadistica (curso, matriculados, notaExcelente, notaRegular, notaDesaprobatoria)

SELECT A.curso,
     count(A.*),
     (SELECT COUNT(*) FROM Nota WHERE Curso = A.curso AND Nota >8),
     (SELECT COUNT(*) FROM Nota WHERE Curso = A.curso AND Nota BETWEEN 6 AND 8),
     (SELECT COUNT(*) FROM Nota WHERE Curso = A.curso AND Nota < 6)

FROM Nota A
GROUP BY curso