First of all I would like to say that I think Robert has a much harsher public view of public education. I dont think that it is critized as much as he feels. It will always be critiqued because it cost us money but for the most part American are approving of PubEd as he likes to call it.
You talk about the "job" of public education. What is this job becuase I think many times it is not defined. They say in business that the first thing you must do is define success yet I think many school systems have not done this.
The last thing I have to say is that the last parragraph is confusing. A "mediocre private school" would be mediocre on the private school deffinition of success. A mediocre public school would also then only be mediocre on the public school spectrum. Therefore, since the top level public schools will never compete with top level private schools such as McCallie in TN, any mediocre public school will also never compete with its private conterpart. In a private school all the classes are mor rigorous than the public school of equal standing. That is how they earn such a high reputation. The only thing that a private school may lack is diversity, where it happens that the same type of kids aspire for the same things. In a public school there is a more diverse student body with more interests that need to be accomidated. That is all.