Use this:
SELECT
...
...
ORDER BY DECODE(month, 'April', 0, 'May', 1, 'June', 2, 'July', 3, 'August', 4, 'September', 5, 'October', 6, 'November', 7, 'December', 8, 'January', 9, 'February', 10, 'March', 11, 12)
If the month is stored as an integer (e.g. Jan=1, Feb=2,...):
SELECT
...
...
ORDER BY ((month + 9) % 12)