NHibernate Many To Many

Classroom.cs

public class Classroom
    {
        public virtual int RoomNumber { get; set; }
        public virtual IEnumerable<Student> Students { get; set; }
    }

ClassroomMap.cs

public class ClassroomMap : ClassMapping<Classroom>
    {
        public ClassroomMap()
        {
            Bag(x => x.Students, m => m.Table("StudentClassroom"), map => map.ManyToMany(p => p.Class(typeof (Student))));
        }
    }

Student.cs

public class Student
    {
        public virtual string FirstName { get; set; }
        public virtual string LastName { get; set; }
        public virtual IEnumerable<Classroom> Classrooms { get; set; }
    }

StudentMap.cs

public class StudentMap : ClassMapping<Student>
    {
        public StudentMap()
        {
            Bag(x => x.Classrooms, m => m.Table("StudentClassroom"), map => map.ManyToMany(p => p.Class(typeof(Classroom))));
        }
    }