I see no particular evidence that schools or teachers are worse than they once were, or better for that matter. What has changed is that we are less comfortable with students dropping out of school as most once did.Never try and teach a pig to sing: it's a waste of time, and it annoys the pig.Robert A. Heinlein - Time Enough For Love
Our society has changed in ways that leave fewer lawful things for the uneducated to do to earn a living. The uneducated do unlawful things and we end up housing them in prisons for large portions of their lives.
Imprisonment is expensive, so as a matter of social policy we try to get more young people to finish school in order to qualify for lawful jobs. Very often, the attempt fails, and annoys the youngsters who are not pigs, but are more or less ineducable in a formal sense.
A couple of books have emerged which take this viewpoint. Mark Bauerlein has written "The Dumbest Generation" and even more to the point, Robert Weissberg has written "Bad Students, Not Bad Schools." Both are used as sources in this Washington Examiner article by Gregory Kane.
We have converted our public secondary schools into non-residential reform schools and are surprised when they don't succeed in teaching their pupils. Imagine what they could accomplish if, like colleges, they only contained students who wanted to be there.