<p>Few studies have investigated the combined association of lifestyle behaviors on academic achievement. This study explored the independent and cumulative associations of physical activity, sleep, diet, and screen time with academic performance. The sample consisted of 974 grade 8 students (including 262 with attention-deficit/hyperactivity disorder and/or specific learning disorder). Data regarding lifestyle were obtained from two sources: parents reported on sleep, screen time, and diet, while adolescents self-reported their physical activity levels. Additionally, academic performance data were obtained from official school records. Mixed-effects ordinal logistic regression models were used to determine the independent and combined associations of lifestyle behaviors with academic performance, adjusting for demographic confounders and neurodevelopmental disorders (ND). Adolescents with ND exhibited lower grades and met fewer lifestyle behavior recommendations than their peers. After controlling for potential confounders and lifestyle behaviors, our results indicated a positive association between having three meals a day and academic performance. Additionally, adolescents who adhered to the Mediterranean diet received significantly higher grades. Meeting recommendations for sleep and screen time was also related to better academic achievement. Lastly, participants who met 4–5 lifestyle recommendations were more likely to perform better than those meeting only 0–1 recommendation. The present investigation demonstrates that lifestyle behaviors have positive associations with adolescents’ academic performance independent of demographic factors and ND. Meeting recommendations for multiple lifestyle behaviors seems to have a greater effect on educational outcomes than any individual association. Therefore, school-based interventions that target multiple health components may have a stronger association on academic achievement than those focusing on a single lifestyle behavior.</p>