The second biggest teacher's union is the AFT, the American Federation of Teachers (the biggest is the National Education Association, made up of state unions such as the CEA, Connecticut Education Association). They put a powerpoint presentation, "How Connecticut Diffused The Parent Trigger" on their website (in pdf) explaining in detail how they gutted a bill that would have given parents more power over poorly-performing schools. Rather than kill it, they purposely kept it alive but made it empty of meaning.
This is standard stuff, and a good case study for how a business can affect legislation, but the webpage "The AFT’s Real Feelings about Parent Power" criticized it, and it didn't look good that prominent on the slide "What Helped Us" was "Absence of charter school and parent groups
from the table". As I said in class, though, that's central to politics--- if you're unorganized or rationally ignorant, your surplus is weighted less heavily or not at all in politics.