Female teachers mark male pupils more harshly than they do their female students, research has claimed.
Additionally, girls tend to believe male teachers will look upon them more favourably than female teaching staff, but men treat all students the same, regardless of gender.
The study, released on Thursday, told 1,200 students in 29 schools to place financial bets on who would give them higher grades: external examiners or their teacher.
Conducted by professors Amine Ouazad and Lionel Page, for the London School of Economic's Centre for Economic Performance, the report said:
"Male students tend to bet less [money] when assessed by a female teacher than by an external examiner or by a male teacher. This is consistent with female teachers' grading practices; female teachers give lower grades to male students.
"Female students bet more when assessed by a male teacher than when assessed by an external examiner or a female teacher. Female students' behavior is not consistent with male teachers' grading practices, since male teachers tend to reward male students more than female students."
Additionally, the results showed the students' beliefs tended to increase the gender gap in investment and effort. Having a male teacher increased the efforts of female students whereas a female teacher lowered the efforts of boys.
But, more encouragingly, the study found no significant evidence of ethnic discrimination.
"Our results suggest that students from low-income families and minority ethnic backgrounds do not believe in systematic teacher biases. This result is significant given that in some countries, including the United States, studies have found that minority students state beliefs in detrimental teacher biases."