Query To Find Schools With Only Boy/girls

I've been struggling with this one for quite some time now and would appreciate some help:-

I'm trying to get a list of schools that only has male students. the closest I have so far:-


SELECT Schools.SchoolName, FORUM_MEMBERS.M_SEX , COUNT(Schools.SchoolName) AS no_of_students
FROM Schools
INNER JOIN FORUM_MEMBERS ON (Schools.SchoolID = FORUM_MEMBERS.SchoolID)
WHERE (FORUM_MEMBERS.UserType=4)
GROUP BY Schools.SchoolName, FORUM_MEMBERS.M_SEX
ORDER BY Schools.SchoolName, FORUM_MEMBERS.M_SEX;

The result is a list of schools:-
SchoolName, M_SEX, no_of_students
school 1, Male, 11
school 1, Female, 20
school 2, Male, 8
school 2, Female, 1
school 3, Male, 12
school 4, Male, 14
school 5, Male, 8
school 5, Female, 1

But what I really need is schools with only male students:-
SchoolName, M_SEX, no_of_students
school 3, Male, 12
school 4, Male, 14

Many Thanks