American teachers unions are increasingly the target of measures, authored by friends and foes alike, intended to limit their power, or even eviscerate them. Looking at this scene, one would never guess that the countries that are among the top 10 in student performance have some of the strongest teachers unions in the world. Are those unions in some way different from American teachers unions? Do unions elsewhere behave differently from American teachers unions when challenged to do what is necessary to improve student performance? To explore these questions, the author compares teachers and their unions in Ontario, Canada and Finland with their U.S. counterparts. From this comparative description of the development of unions in the United States and northern Europe and the approaches taken to reform in Canada and Finland, the author concludes that the current impulse to curtail the influence of the teachers unions may return some powers to management that over the years have gravitated to the unions. But that victory is likely to come at the price of deeply alienating many teachers from the larger cause of education reform.