I don’t really think the end goal of the average teacher is to dumb down children. I DO think forced curriculum outside of parental control DOES tend to have that effect - especially when the hidden agenda is to produce cohorts ignorant of their national origins and freedoms. Teaachers, in general, want their students to succeed. However, the direction of modern education is to produce ‘world citizens’ fitted for the economic needs of the world government - not patriots of liberty-loving, self-motivated individuals.
I think the average teacher is good at heart. But then they are required to teach to ‘the plan’, using approved books, and an easy plan makes for easy teaching. The central control and planning of education is already here. Just pick up a modern text on science and read what it says about global warming.
So no, I don’t ascribe motive to the teachers, just the system they work in.
When I was in school, I still remember a single teacher who I had, he formed my life’s goals significantly, he told me something like ‘only the loser stops at the requirements’. He always had extra credit textbooks and tasks for students to do. Stuart Cady was his name ... Long since passed away.