ANY school is really just what the student and the parent make of it. If the student is motivated to learn they will. You've made a good point about parents...there are way too many that don't take education seriously. I actually had a parent tell me when I commented about their child's lack of homework completion at a meeting, "Oh, "Steve" can't wast his time at night doing homework. He's in school all day, he has to have some free time, after all, he's only 14."
The big difference is...private schools can choose who they educate and take only the "creme of the crop", public schools have to educate everyone. Going to a private school guarentees no more success than going to a public school. It sometimes appears that private school students are more successful because they just get rid of those who are not performing to the standard they expect. There are some cases where this does not happen, the student stays at the school despite the problems and receives passing grades for substandard work...usually there is a financial reason for this.
You mentioned something about a sort of "tracking" that used to take place , there is a lot less of that now...most classes are multi-level. In High School there is a little more division, but NOT like it was when I was in school. As you probably know, I teach 8th grade Special Education. These students have REAL problems, it's not like it used to be, they can not put a kid into special ed just because they are lazy. There is a long list of criteria that a student must meet and there has to be evidence (tests) to prove the disability before a student can be placed in special ed. My students are those with specific and identified learning disibilities...they are not cognitively impaired. The average IQ in my room is right around 110.
Maybe it's just me, but my students use the same exact materials as others at the grade level. We cover the material at a different rate and using different methods, but the content is the same. My students take the same MCAS test as everyone else too. Granted, they may have some accomodations, for example, there are a few that can use a word processor with spell check (their spelling is not what is being tested). I have to justify each and every accomodation made and that accomodation has to be something that is available to the student on a day-to-day basis.
Thank you for pointing out that one of the main problems with public education is the parents. I used to work in the primary grades (because I was assigned there). There was nothing sadder than giving a Kindergarten screening and have a child come in that didn't know their colors, couldn't count to 10, didn't know the alphabet and in some cases didn't even know their address or their last name. When we asked parents about this many would say, "that's not our job, that's why we send them to school." The VALUE of education starts in the home and needs to start early. (sorry, I had to rant)