The director of the Demos think-tank joined workshops to ask teachers about their jobs and the future of their profession. "I was genuinely surprised by the degree of pent-up grievance," he said.
"Even those fully committed to doing a professional job, meeting high standards and fitting in with the agenda had this sense of not having been listened to and that people didn't really know what it was like."
A high proportion said they had never before been asked to take part in this kind of discussion - either during national reforms or as part of the running of their own schools.
And, he said, there was a "righteous anger and a sense of injustice" that the public still thought they clocked off at 3.30pm and enjoyed long holidays.
"They felt the amount of paperwork they took home was at a level that highly-paid senior executives should be working at."
Researchers visited 10 schools, spoke to 150 teachers in workshops and conducted a postal survey. Mr Bentley said: "There's very little sense that teachers have been included in the wider debate.
"Among many there's a weariness, often combined with a slightly surpressed sense of anger. They were told to teach one way for eight years and now they're told it's wrong and it's their fault."
The ever-growing workload was also taking its toll. "Quite a lot commented on the sheer exhaustion."
Older teachers were more interested in improving working conditions than their pay. Younger teachers were more flexible about change. "But they were still unhappy about the lack of autonomy." With changing working patterns, few saw teaching as a career for life - but pay and burn-out were also factors.