But one course at the university's latest summer school has a very different requirement - no-one can attempt it without having previously failed.
Last year 1900 students, including 1400 studying health sciences, attempted the paper, chemistry 191, during the usual academic year.
This paper is a prerequisite for later study in medicine and several other major study programmes.
The paper's pass rate was 75%, and, accordingly, about 475 students failed.
But a remarkable thing happens at summer school.
Last year the school's pass rate for the same paper, among those who had previously failed, was about 90%.
Success enables students to study many otherwise unavailable scientific courses, including those in health sciences.
This summer nearly 100 people are trying again. Lectures for the summer paper are given by Associate Prof Barrie Peake (67), a senior academic who has been teaching such chemistry papers for more than 40 years, and by professional practice fellow Dr Dave Warren (55).
Offering the paper again over summer was suggested by sciences division administration manager Bryan Johnston, and had proved successful over the past seven years, the teachers said.
Several factors contributed to the greater second-time success, including that the students were more familiar with the university system, and had developed better study habits.
Teaching and learning were also undertaken more intensively, and lower student numbers allowed more study support.
Seeing the students succeeding was ''very, very rewarding and satisfying'', Dr Warren said.
Prof Peake also greatly enjoyed the teaching and giving students the chance to ''really kick-start'' further study and career opportunities by passing the paper while maintaining high academic standards.
The Otago physics department also offers a second-chance paper.
The 15th annual six-week summer school started last week.