Kids, who are physically fit, perform well at school, according to a new study.

The researchers found that students who were physically fit scored better on standardized math and English tests than their less fit peers.

They analysed the relationship between physical fitness and academic achievement in a racially and economically diverse urban public school district of children enrolled in grades 4 - 8 during the 2004 - 2005 academic year.

They found that there is a significant relationship between students' academic achievement and physical fitness.

The odds of passing both standardized math and English tests increased as the number of fitness tests passed increased, even when controlling for gender, race/ethnicity, and socio-economic status.

"For families and schools, these results suggest investments of time and resources in physical activity and fitness training may not detract from academic achievement in core subjects, and, may even be beneficial," the authors said.