This research examined the impact of students' characteristics and their perceptions about learning environment on mathematics and science achievement. It specifically aimed to demystify the effect of gender, economic, social and cultural status, immigrant background, teacher feedback, teacher support, exposure to bullying, and disciplinary climate on on mathematics and science achievement. Furthermore, it reanalyzed the results of the 2018 PISA-Saudi Arabia. Economic Social and Cultural Status, Gender, Teacher Support, and Immigrant Background found to have an influence on mathematics and science achievement. The study recommended that educational institutions in Saudi Arabia should pay attention to gender differences and the economic, social and cultural status, and immigrant backgrounds of students.