It's all over the map, and there are hardworking teachers. I can tell you about my experience in the 90's. There were exceptions, but generally teachers I had

It's all over the map, and there are hardworking teachers. I can tell you about my experience in the 90's. There were exceptions, but generally teachers I had would hand out worksheets and assignments, and then class time would be spent doing what was effectively homework. Very rarely would there be an actual lecture. I had several completely incompetent teachers as well, who were completely tolerated by the schools administration. One teacher, Mrs. Rushing, was completely incompetent. During the lesson on vector addition, she claimed that if you added a bunch of vectors together, it was the same as taking a vector from the beginning of the first vector to the end of the last vector, if you put the source of each vector at the end of the previous one. Well, that's what she was meant to say, she actually insisted that the length of the paths was the same, and she argued for it despite it being obviously wrong. She had at best a weak and often incorrect understanding of the material she was meant to be teaching. She also used her entire planning period each day to sell Avon or Mary Kay or something, which I witnessed every day as I was an aid in the math department and was in the planning room during her planning period. Every day some random lady would come in to the school and chat with her for an hour and try cosmetics during the time she was meant to be preparing for classes. During class she would often get stuck and go ask other teachers questions mid class. So it would have been great if they had tested the outcomes of the students who were in her class, and compared them to the several wonderful teachers teaching the same subject at the same school. Instead, she is still there.