I hafta say this question is a little outside my usual scope but I'll just share what I know of the Ming's civil service exam policy.
TLDR : Pretty much the same thing as college today. You have to know the dean or make a sizable donation to the library or hire the best tutors to get that scholarship.
I assume you mean the jinshi which was the Ming Chinese term for the imperial civil service exams and their notoriously high failure rate. Strictly speaking, it was actually three exams,held every 3 years; the provincial examinations (xiangshi), the metropolitan examination (huishi) and the palace examinations (tingshi). Infamous for the high number of failed candidates and the startling number of applicants (2-3 million applicants each time with 1000 odd fellows passing on a good cycle),it stands as a hallmark of the "political meritocracy" that Late Imperial China is so famous for. Indeed,the first Europeans like Ricci who visited Ming China proper (Catholic Jesuit mercenaries) often held praise for the civil service examinations and the empire wide school network,which was something hitherto unseen in Europe. Juan González de Mendoza,author of Historia de la China,calls it a “Mightie Kingdome” specifically for this reason ;its rational policies and enlightened education.
State expenditure on education was primarily focused on actually organizing the exams and in organizing "scholar offices" like the Hanlin academy and the Ming era creation,the Bureau of Translators (四夷館). I'd like to say they were something like a pHD research lab,but,in truth,they functioned more as a think-tank,with nobles or newly affluent merchants often coming to find a literary clique to attach to like a barnacle. The Hanlin academy was a sorta "holding ground" before someone went into actual civil service,with the honorary title of shujishi (庶吉士).The Ming had an enormous bureaucracy and spent accordingly.When compared to some 500 Song and 400 Yuan dynasty private academies, the Ming overall had in place some 1000 to 2000 such academies by its end.
Ok that's all the fluff done. Now let's get to the modern-day explanation. So,there're probably two reasons why the civil service exam pass rate was so low. The first is because of the curriculum.There was basic school and advanced rich school and,to pass,you really needed to be rich. Contrary to what the Europeans imagined,education in Ming China wasn't entirely a state meritocracy with private learning being equally as important. The guys who passed were,very often,the guys who could hire the best private tutors.
Money and Education
Wealthy merchants and nobility would hire famous tutors (often scholars who actually managed to pass the exam) to tutor their sons with their own money. Education was such a thing for the gentry that the opening of academies to include more commoners by Wang Yangming (1472–1529) during his tenure as governor of Jiangxi was considered a big reform by the Ming court. Moreover,the general impression that the Ming elite held of education was its association with social political order ie that the educated were best suited to rule over the illiterate and were wary about wanton dissemination of education among the common populace.
State academies existed,of course, and long before the Ming, but taught a classical curriculum. It emphasized the ancient Chinese classics and the values they expounded,the importance of the meaning behind the four books and the five classics sishuwujing ( 四書五經 ) but actual learning by the literati often involved about six interrelated aspects: poetic, political, social,historical, natural, and metaphysical,most of which would only be taught by an experienced tutor who had "gone through the wringing" of the actual examination,so to speak. The state academies,open to anyone who could afford school fees, were thoroughly incapable of providing a holistic education for anyone wanting to pass the Civil Service exam and,in time,became more of a testing center for memorization than an actual place of learning. Moreover, it was dreadfully boring and only taught the classics. In 1370,the Ming removed poetry,the favorite past-time of any would-be scholar from the curriculum and it would not be reinstated till 1756,by the Qing,making the state academies a purely servile and dry affair. Expensive private tutors,however, could select their own curriculum and were hence always more popular. Of the millions of hopeful applicants every year,only a select handful were lucky enough to be rich to afford such an advantage and this shows in the pass-rates. As for the reason why a hopeful examinee would need to learn poetry to pass despite it being removed from testing,it's perhaps best described in the 2nd reason...