Teachers' union "insanity"

As an ad hoc faculty I am sensitive to education/employment issues, but my unpaid teaching job does not blind me to the idiocy of teacher unions. Seems the teachers who teach advanced placement courses in Boston were eligible for performance based bonuses based upon the number of students who passed the AP tests. The schools which used the bonus system saw a 39% increase in passage. But the Teachers' union complained, not about the bonus, rather that the recipients were the teachers teaching the AP courses. The union wanted all teachers to share in the bonus irrespective of their efforts at teaching the AP students.