The one big difference between Europe ( and successful American vs. failed public schools), is discipline via parental attitudes. Therefore, any comparison studies would have to control that factor to result in a valid conclusion.
There are successful American schools just as there are failed American schools. What is not productive, is to think one has insight relative to the problem, with actually sitting in the class rooms as an adult and observing what is actually taking place and postulate "solutions".
Actual occurrence: Female student given one day "time out" as the only punishment for holding a pencil on a kid's seat which cause the kid to impale himself when he sat down. This was not the result of "g" schools, teacher unions, etc. It was the result of an inept administrator following the perceived wishes of the system of minimizing the events that would show how out of control the students are.
One big difference between European schools and the US schools is that one, kids are expected to have discipline, and to demonstrate some respect toward teachers. . .teachers are "almost always" right in the eyes of the parents. . .contrary to "blame the teachers" here. Unfortunately, even that has decreased in Europe as well.
Another major difference is LESS HYPOCRISY! Europeans do not pretend to believe that "no kids can be left behind," and that "every kid should graduate with a high schoold degree!"
Every kid is obviously welcome (and even obliged) to go to school, however, a determination of "intellectual abilities" versus "technical" or "artistic" abilities is done at a much earlier age. Even before entering middle school, there is already a test where kids compete against every kid in the whole huge district (it was about 900 kids when I took it).
Then, in middle school already, kids have a choice (based on demonstrated abilities) between about 5 or 6 different tracts. . from very highly academic, to more basic. If a kid cannot follow the work (even in elementary school), he/she is not automatically passed to the next grade, but is held back. . .even twice if necessary. It is not unusual (probably about 10% of kids are held back at leats once), so it isn't as stygmatizing.
Another test is done at the end for the 3 years of middle school and at that time, the least academicly inclined kids are given a choice between several "apprenticeship" type of opportunities, which consist of some easier academics, and on the job training (i.e., carpentry, hair dressing, plumbing, mechanic). Other kids with more academic abilities are divided further toward 3 years technical schools, or 3 years academic schools. . .
Only the two or three top academic selections will lead automatically to college. However, kids are not entirely penalized for "late blooming" or for delayed intellectual development, and an "entrance" exam to college can be taken by ANY kid, but must be successful before allowing a kid to enter college or "schools of higher learning."
Basically, a kid who has no interest in college, doesn't have to waste his/her etime until he/she is 18 taking under water basket weaving classes, but can take functional classes that will assure that he/she will come out of high school with a trade which will allow him/her to get into the work force immediately with a fully developped skill.
The top 3 or 4 "academic" paths in high school prepare kids A LOT better than our regular high school for college. In fact, any European kid who finished high school is admitted immediately into the second year of college in US universities, and high school kids from the US who have successfully completed one year or more of high school in Europe are also given college credit in the US.
I entered the university in the US after being out of school (in Europe) for 25 years. . .I had no college in Europe, and yet I was able to not only compete but get a 3.9 point average, carrying a double major, and graduating in 4 years. NOT because I'm smart, but because I had an excellent preparation and study habits. . .and I was motivated as a "re-entry" student.