Research was carried out with 253 teachers in the province to investigate their knowledge of the subject they are teaching.
Teachers got an average mark of 57 percent, and a quarter of them got below 39 percent.
The research was published in the "Perspectives in Education Journal" in March and authored by Thokozani Mkhwanazi and Sarah Bansilal from the University of KwaZulu-Natal, and Deonarain Brijlall from the Durban University of Technology.
The difficulty of questions in a maths exam is broken down into four levels, with level four being the most challenging.
The teachers who wrote the test managed an average of 26 percent on level four questions, which made researchers question how they could be teaching their pupils.
"The results of this study raise concerns about the teaching of maths by (Grade 10 to 12) teachers whose knowledge is so poor," the researchers were quoted as saying.