I don't know if we can pin it down to a particular event, but I personally believe it began the first time a parent sued a school district and won. From that point on, it seems that teachers are no longer respected or appreciated. Money plays a big part too. People outside of education believe that teachers work 8 months out of the year, get out of work early, get summers off, and make tons of money. Nationally, I do not believe teacher are well-paid. Those districts that are lucky enough to be paid commensurate with the effort and work they invest are fortunate indeed. Teaching is no longer about content. It's teaching to the test; it's arguing with students about why they have to listen to you; it's comforting students whose peers have been emotionally abusive; it's advocating for students who believe they are being lost in the system; it's trying to get parents to care about their child's education through emails, letters, phone calls and meetings. It's tutoring after school. It's going the extra mile with students that need someone to talk to...and you do it willingly on prep. time and during lunch periods when you ought to be grading papers or making copies, or phone calls home to parents. It's trying to hold onto your dignity while receiving verbal abuse and disrespect from parents and their children. It's working your hardest when your administration does not support you, and listening to complaints about teachers because of the bad ones that get in and never leave.
And it's finding the energy to still get out of bed when it's dark to prepare to teach and mold a generation of kids who need to not only survive, but have families and shape the world of tomorrow.
It's happened as the school board lies to the media; as they put students that learn on different levels into one classroom because it saves money—and school board members want to be re-elected. It happens when teachers act unprofessionally or carry on illegal and/or immoral behavior where kids are concerned, giving all teachers a bad name.
When education became something to be questioned, and education became a right rather than a privilege, the tide turned against teachers. Though teachers are most often treated as if they are at the bottom of the educational food chain, the teacher is the one who sees a student on a more regular basis than many parent(s), and may be the only person in a day who shows concern for that child. It has also come as parents and students refuse to assume responsibility for their actions and look for someone to blame. It's easy to blame the teacher with five classes of 30+ students in each one; but it's done without any knowledge of what it takes to teach the student and care about him/her at the same time. Because for good teachers, it's not a job (as the media, school boards and public would have everyone believe); it's a calling. And trying to work to unrealistic expectations often interferes with a teaher's family life, time spent with his/her own children and his/her health. If every parent spent one or two days shadowing a teacher in a school year, I really believe that a lot of the mythology would disappear.
When it stopped being about kids and their learning, that is when everything went wrong. I don't know if it can be fixed.