I went to an excellent public school. I know I will probably get flamed for saying that, since many of you think that's an oxymoron, but it's true. There are good public schools.
I will tell you one "basic" thing that differs from good/bad schools of the present/past: present emphasis = non-directive education = bad; past emphasis = sound and traditional methods = good.
If the method of education used is non-directive education [also called OBE (outcome based education) or affective education, and an ever-changing list of other "names"--you can guess why that's done], which is based on HUMANISTIC PSYCHOLOGY, instead of sound and proven methods [i.e., the traditional methods of teaching by "rote" (memorization), phonics, memorizing math tables, spelling tests, etc.], then, as a general rule, the education received by the student is poor because the emphasis is no longer on learning.
Because of Humanistic Psychology, the teaching methods shifted from learning the basics to an emphasis on FEELINGS and self-esteem.
By the above standard, I received an excellent education at public school. There was no psychological manipulation on how I thought and felt. Instead, the focus was on learning grammar, spelling, memorizing multiplication tables, phonics (instead of the "whole language" approach--which is a proven failure with the majority of children and why California finally dumped the method, no longer allowing its exclusive use and went back to including phonics instruction), history, geography, music, etc.
When attending college as an adult (many years after high school), I was appalled at the poor education received by my "peers" (most noticeable with those who were 10 years + younger than me). Many were placed in remedial classes (including the one in which I was a teacher's assistant (English)), where I learned that most had no understanding whatsoever of grammar; didn't have a clue what a complete sentence was; had atrocious spelling; didn't know how to sound out new words using PHONICS.
The current "system" being used continues to be based on a failed system: non-directive education. And this approach is how new teachers are trained in the teachers' colleges, who, BTW, are products of "it" being used on them.
I agree with BRMG. I would like to see how you defined good. I went to a very small public school growing up. I was not challenged until I got into highschool, which means I spent a lot of time in trouble in the lower grades.
Secondly, I had some phenomenal teachers in highschool. They wanted more than anything for me to learn, and to open doors & horizons for me. But, I still had to deal with the social antics of peers, which completely offset what the teachers were doing.
Teen pregnancies were rampant (and this was a small school, everyones' parents went to church); drug and alcohol use were everywhere. Just run out to someone's pickup.
A few years ago, I interacted with my nephew going thru the same school. His skills were minimal compared to what I had by his age. And all of the rest of the "fun" stuff still existed.
Comparing my experience to his, I would say the public school I went to was good. Yet, I left it knowing I would never subject my kids to that atmosphere. And, when I left, I had teachers who knew I would never support public schools again. I had one teacher in particular who wrote a message in my senior year book to not give up on public schools yet.