Background: Sedentary behavior and low levels of physical activity may predispose youth to increased risk of obesity and other chronic diseases in adulthood (3). Although research has shown lower educational achievement among adults with obesity, little is known whether the same association holds for children and adolescents (4). As recommended by the 2008 Physical Activity Guidelines Advisory Committee, one of the top research needs regarding the health benefits of physical activity among youth is to investigate the association between physical activity and academic achievement in children and adolescents (5). However, the guidelines do not specifically highlight the need to reduce sedentary behavior in terms of academic achievement, which is important given that children can be excessively sedentary while meeting the physical activity guidelines (6).

Purpose: To examine the association between sedentary behavior and academic performance in early adolescence.

Study Sample:

- Children ages 11-yr and 13-yr old

Dependent Variable:

- National tests of academic performance/achievement

- Key stage 2&3 assessments- standardized test scores in English, Math, and Science

- National curriculum level awarded in English, Math, and Science tests

- Total marks achieved in English, Math, and Science tests

- Tiers at which the exam was taken (for Math and Science)

Independent Variable:

- Sedentary behavior [accelerometer; mins/d less than 200cpm]

Covariates:

- Moderate-to-vigorous physical activity (MVPA) [accelerometer; minds/d >=3,600]

- Obesity [Percentiles: 90th (obese), 80th (overweight), 10-79th (normal)]

- BMI/DXA

- Child's birth weight

- Child's head circumference at birth

- Parental education

- Parental occupation

- Length of gestation

- Mother's age at birth of study child

- Mother breastfed

- Mother's smoking status during pregnancy

Data Analysis:

- Raw scores achieved in English, Math, and Science will be recalibrated using information from the key stage level achieved and the tier at which the exam was taken (for Math and Science) to obtain a transformed score in fraction of a level (method developed by Levacic et al. 2005. The same approach was also used by Leon Feinstein and Ricardo Sabates in their ALSPAC project entitled "Impact of adult learning on their children's school attainment").

- The transformations of the Math and Science scores are important because it takes into account the tier at which pupils enter the exam and their potential influence on the maximum score.

- Results will be interpreted as the amount of progress made by the student in months or years.

- Ordinary Least Squares (OLS) regression techniques, all regressions will be performed separately for English, Math, and Science test scores.