How Do Teachers Feel About Being Forced to Pay Dues to Unions?

From today's Wall St. Journal:
We asked a representative sample of 3,300 members of the general public and approximately 700 teachers the following question: “In some states, all teachers must pay fees for union representation even if they choose not to join the union. Some say that all teachers should have to contribute to the union because they all get the pay and benefits the union negotiates with the school board. Others say teachers should have the freedom to choose whether or not to pay the union. Do you support or oppose requiring all teachers to pay these fees even if they do not join the union?” (To avoid stacking the deck, the order of the arguments for and against the policy were randomized.) 
Only 34% of the public support agency fees, while 43% oppose them. The remaining 23% declined to take a position. If this latter group are put to one side, a clear majority, 56%, favor ending the union shop. That finding is consistent with the public’s overall opinion of teachers unions, we found—as only 30% say they have had a positive effect on schools and 39% say they have a negative effect. 
The more startling results came from the teachers. Only 38% of teachers favor the agency fee, while 50% oppose it, with the remaining 13% expressing no opinion. In other words, 57% of teachers with an opinion on agency fees disagree with the American Federation of Teachers and the National Education Association.