Girls, who outperform boys in English at every stage at school, are unaffected by the number of boys in their English classes.
Girls also do better when there are some boys who receive free school meals in their class, Proud found.
He said: "The results imply that boys would benefit at all ages from being taught English with as small a proportion of girls as possible. In maths and science, the results tend to imply that both boys and girls benefit from having more girls in the classroom. A mix of the genders in both science and maths is optimal."
Proud said boys may do worse in English when there is a high proportion of girls in their class because they realise that the girls are better than them. It could also be that teachers use teaching styles more appropriate to girls when there are more girls than boys in the class. Both genders perform better in maths and science at primary school when there are more girls in the class because boys tend to disrupt the class more, he said.
Professor Alan Smithers, director of the Centre for Education and Employment Research at the University of Buckingham, said girls started school with slightly better verbal skills, while boys started with a slightly greater aptitude for maths.
"Boys might be discouraged by how well girls are doing in English," he said, "but that still does not explain why they would do better in maths and science with a higher proportion of girls in their class.
"This is one study, among many, which detects very small differences between boys and girls. But you can't say that it means boys or girls should be separated. It has very little practical importance for schools."
研究发现，当班上女生人数较多时，男生的英语成绩要下降10%，而女生们的成绩则不受影响。
研究人员今天宣称，当班上女生人数较多时，男生的英语就会学得较差。而人们以往普遍认为，在学校中，女生对男生总是有积极影响。
布里斯托大学的研究生Steven Proud将在皇家经济学会的回忆上宣布：小学与初中的英语课上，女生越少，男生成绩越好。
然而Steven Proud同时发现在数学与科学学科上，女生人数多对男女生都有积极影响——成绩提高10%。
在2002年至2004年间，Proud为了完成他的博士研究课题，跟踪查询了英格兰16000所学校中7岁、11岁、14岁、16岁的男女生测试成绩。
为了研究女生所占比例对所有学生的数学、科学以及英语成绩的影响，他对测试分数进行了分析。
男生数目比女生数目要稍多一些，但是在大多数学校的班级中，两性比例是基本平分的。Proud研究的对象是那些女生所占比例超低或者超高的学校。
Pround发现，相比于班上没有或者很少女生之时，当班上女生人数较多时，男生的英语成绩总是会下降10%。
特别是在小学校中，女生越多，男生的英语就学得越差，Proud同时发现。