The problem is that many factors other than school quality can affect student performance. Intelligence is obviously one important element, but there are many others. Let's look at a few.
A major factor is parental income . Children in low income families are likely to be handicapped in a number of ways. Their parents, usually poorly educated themselves, are seldom good role models, are unlikely to inspire them to work hard, or to help them with their studies. Very few of these children start their schooling with some initial reading skills, or even the kind of eagerness to learn to read that often comes from having had stories read to them by parents. Many, whose families live in cramped quarters, do not have adequate places at home where they can study and do homework in peace. Bad eating habits and poor nutrition further hinder their ability to concentrate on schoolwork. Alcohol and drug abuse cause further problems.
An important factor undermining motivation is peer pressure. Particularly among boys, there may be a widely shared attitude in some groups that doing well scholastically is not "cool". Good students may be mocked by classmates. This attitude encourages many students to neglect their studies, and to treat exams frivolously, including IQ tests. This can be a problem in all income brackets, but is most serious at the low end.
Problems accumulate. A student who, in the lowest grades, falls behind in reading is going to have increasing trouble in just about every subject. Mathematics is a subject in which each topic is a building block for subsequent topics. So early failures in comprehension are hard to overcome. This also leads to later difficulties in science courses. Some high school students from poor families have part time jobs that reduce the time and energy that they can devote to school work.
The effect of all these factors is that schools with a large proportion of children from poor families are likely to look relatively bad in terms of student academic performance, no matter how good the teachers and administrators are. Some racial or ethnic groups are over-represented in the lowest income brackets.
Note tho that not all students from poor families succumb to the above problems. Some children from the worst family backgrounds overcome all handicaps to excel in school. On the other hand, there are some middle class students with attitudes and behavior problems quite similar to those sketched above. Nevertheless, a school serving a predominantly poor population must cope with a far larger proportion of students handicapped by these problems than a school whose students body is largely drawn from the middle class. And many, if not most, of these problems are not susceptible to solutions confined to schools.
There are a number of alternatives to public schools. Parochial schools, and a variety of types of private schools have long served many children. Home schooling is another option.
Each type of schooling, including public schools, comes in a variety of flavors. Some high schools specialize in one or more subjects, such as music, or science, or technology. Teaching philosophies differ. In recent years, much use has been made of computers and the internet in various ways. Financing ranges from conventionally operated public schools to schools funded entirely by tuition fees, to mixtures of government subsidies, tuition, and subsidies by private foundations. In virtually every category quality appears to range from very poor to excellent; often there are differences of opinion as to how good a school is. As indicated above, it is not easy to evaluate schools because student performance is sensitive to so many factors not under the control of the schools.
In my judgment our public elementary schools are generally weak in math, and history is badly handled at all levels. I doubt that non-public schools do any better in these subjects. There is no good evidence of a general deterioration of the quality of American public schools. In general, they seem to compare favorably with schools in most other industrialized countries, when student income categories are taken into account. But, for several decades, American public schools have been harshly criticized, and the idea of privatizing schools has been vigorously promoted.
The attack on schools coincides with a general privatization movement. The US Postal Service was an early target that has been significantly weakened, mainly by allowing private corporations to skim off the most profitable services. Private prisons are now big business . Water systems have been privatized in many areas. Flight Service Stations, providing weather and navigation information services to pilots, previously operated by the FAA (Federal Aviation Administration), were contracted out to Lockheed Martin in 2005. Perhaps the most dramatic instance of privatization of traditional governmental functions are the companies supplying mercenaries, many, if not most of whom, are not Americans, to the military , and the outsourcing of a substantial portion of the functions of various intelligence agencies, including the CIA and NSA . Within the US, there are many more armed guards employed by private security firms than there are police officers .
Public school systems vary in quality, because people in some places do a better job than others of electing good school boards and providing adequate funding; and because, as discussed above, it is more difficult to educate the children of the poor. Private schools of various types also vary greatly in quality.
Starting about two decades ago, a major tactic used to attack public schools has been the charter school concept, whereby tax money is diverted from public schools to privately run, often for-profit, charter schools . This is in addition to the more traditional path whereby parents, at their own expense, send their children to private or parochial schools. Identifying a charter school as for-profit is not simple, because many charter schools, while operated by not-for-profit organizations, contract out almost all operational functions to private, for-profit, corporations. Laws pertaining to charter schools differ significantly from state to state.
About 85% of American children attend conventional public schools,
Roughly 8% attend private or parochial schools, about 5% attend charter schools, and about 2% are home schooled .