The thinking mode of the three science subjects of physics, chemistry and biology is similar, the difference in thinking ability is obvious, the influence of investment is less, and the chance of achievement is smaller, and the top students are more willing to choose. Relying more on the talent of scientific thinking, it is simpler for them, and it is easy to establish an absolute advantage.
Compared with the top students who gather in physics, chemistry and biology, students at the lower middle and lower levels do not have the advantage of science thinking, but are liberal arts with an input and a harvest, and have a more input-output ratio.
Most high schools are also willing to set the strongest class as a physicochemical student, so that the eugenic results can be more presented.
At the same time, the class type ratio of many schools also guides students with low grades to choose physical and chemical students, except for private schools to recruit teachers according to students' course selection, and public schools arrange classes according to teachers, and the number of students who intend to liberal arts will be significantly less than that of science, but the number of liberal arts teachers is not so.
If classes are arranged solely according to students' intentions, there will be a shortage of science teachers and a surplus of liberal arts teachers. In this case, if there are 150 science students in the class, but 200 people choose them, the last 50 will be transferred to other combinations.
It is not uncommon for students who cannot enter the key classes to achieve far worse grades than most of the key classes. Therefore, the selection of subjects in the first semester of the first semester of high school can also be regarded as a hierarchical selection.