Everyone makes mistakes, but what happens when the mistakes could affect thousands of young people's lives? That's the question being asked this week in South Korea, where an error in the national college entrance exam led to the resignation from the country's top exam chief, and an apology to the nation from the education minister.

The two errors occurred in the English language section and the biology section of the College Scholastic Ability Test (CSAT), known colloquially in South Korea as the Suneung. Almost 650,000 people across the country had taken the test on Nov. 13.

According to the Korea Times, question 25 of the English-language section asked students to look at a chart about American teenagers' social media use and choose the option below that was not correct. Students were supposed to choose option five, which read: "Compared to 2006, 2012 recorded an 18 percent increase in the category of cell phone numbers." However, some of the students reasoned it must be incorrect, as it should have said "18 percentage points" and not "18 percent."

In the biology test, students were questioned about the production of an enzyme that breaks down lactose into glucose in wild-type Escherichia coli, according to the Korean Herald. They were then asked to select the correct description of the enzyme, but experts disagree whether there was one correct answer, or two.

From the descriptions given, there is a degree of ambiguity here, and in a test as important as the Suneung, that ambiguity is a problem. Following a public outcry over the questions, the South Korean government announced it would accept multiple answers for the disputed questions. The decision may change the grades of thousands of students, potentially affecting where many will end up studying.

The CSAT is the rough equivalent of the SATs taken in the United States, though its place in society is probably more important. Here's how the Economist characterized the cultural importance last year:

The five-part, multiple-choice admissions test is the quintessence of Korea’s Confucian passion for education, which stretches back to the Goryeo and Chosun dynasties—and hangovers from that time abound. A traditional sweet, known asyeot, and other sticky treats, such as rice cakes and chocolate, are given to students for luck, and sometimes plastered on school gates. That harks back to gwago, a civil-service exam that flourished in the Chosun era, when the names of successful candidates were posted on government buildings. Suneung takers are therefore encouraged to “stick it”, (though the English word fighting!, a Korean rallying cry, is now equally popular). The specific term used to pass the exam—keubchae—is from Chosun times too. And the importance of the state-administered exam has barely diminished since those days; in a country where some 75% of high-school-leavers go on to university, many deem the test the chief battle in ibshichonchaeng: entrance-exam war. Every year, just 2% get into Korea’s prestigious SKY universities, whose nickname is an acronym for Seoul National University, Korea University and Yonsei University.

The test is only given once a year, and that day is a big deal for everyone in South Korea: Planes are grounded during the listening test and public offices open late in a bid to avoid traffic jams. The seriousness with which the test is taken shows why it can be controversial: It may be admirably meritocratic and South Korean's education system ranks highly in international comparisons, but many people feel that the CSAT ends up having too much control over people's lives.

This isn't the first time that the questions in the test have been called into question. In October, the Education Ministry accepted a court decision that found that a 2013 question in the geology section was flawed, and said it would work with the more than 10,000 students affected. The Korean Herald reports that since 2000 four other questions have been challenged and proven wrong.

Kim Sung-Hoon, head of the Korea Institute for Curriculum and Evaluation (KICE), the body that administers the exam, resigned on Monday. He became the third KICE head to resign due to problems with the test. "We did our best this year to prevent erroneous questions," Kim told reporters, "but again there were faulty questions, causing chaos and inconvenience among exam takers, their parents and teachers."