Girls 'get higher marks at school than boys because they are better behaved' International study suggests bias could affect boys' self-esteem Lower marks 'could cause pupils to limit their ambitions' Girls receive better marks at school than boys because they are better behaved, not because they are more intelligent, a study suggests. Teachers give higher marks to reflect 'certain student characteristics' that are not related to ability, the international study claims. The Organisation for Economic Co-operation and Development, which carried out the research, said that the bias could have 'far-reaching effects' for boys' self-esteem. The bias towards girls could have 'far-reaching effects' on boys' self-esteem, researchers said It could also cause them to miss out on university places or change their career ambitions, as lower marks may cause students to lower their aims accordingly. The study, which analysed 17 countries that use a large number of tests set by teachers or student coursework, also found that pupils from affluent backgrounds were given higher marks by teachers during internal assessments. In Britain, nearly two thirds of girls achieve five good GCSEs, while only half of boys do so. The Coalition Government plans to assess GCSEs almost entirely through end-of-year exams instead of coursework marked by teachers. Andreas Schleicher, deputy director for education and skills at the OECD, told the Telegraph: 'School marks are more than just a source of anxiety - and pride - among students. 'Therefore, whenever teachers reward - or punish - certain students' characteristics that are unrelated to learning, they may inadvertently shape a student's future according to factors that have nothing to do with their abilities, talents and personal goals.' Previous research in the United States claimed that girls tended to have traits that made them more likely to impress their teachers, such as eagerness and good organisational skills. Girls receive higher marks from teachers because they are well-behaved, according to an international study The American study, published in the Journal of Human Resources, looked at the performance of more than 5,800 children from the ages of six to 12 in reading, maths and science. Researchers compared pupils' test scores with teachers' assessments of their performance, and found that even from the beginning of school boys' grades are lower than one would predict from their tests alone. The study by researchers from the University of Georgia and Columbia University blamed the discrepancy on the fact that teachers take into account how well each child is engaged in the classroom, how often the child externalises or internalises problems, how often the child loses control and how well the child develops interpersonal skills.