高考 is an unfortunate product of a cutthroat meritocracy. It is literally the only criterion to determine your college admissions in China.
There are explicit affirmative action programs like others have pointed out to try to level the playing field across the country. So for example, if you are a Ughyur in Xinjiang or a Tibetan in Tibet, then your score is curved up. This is similar to how the one child policy only really applied to the urban Han Chinese population.
There were cottage industries of tutoring and extracurricular enrichment that afforded wealthier families better chances for their children. There were also districts with extremely inflated housing prices where the best schools were. The government has now abolished both of these things. Now students are just in school all the time as the after-school tutoring programs have become socialized and compulsory. Still, there is a game of cat-and-mouse.
My overall thesis here is that a mostly level playing field for the children of a country with more than a billion people whose families until recently had a single child to carry their lineage results in a level of pressure that is beyond comparison. However, I still believe this system is far superior to other states where the class system is fossilized and the pressure is lower because the results are predetermined.