This study examined 86 high school (Year 11) students’ basic proficiencies in Mathematics were examined, and the connections between language proficiency, gender, family socio-economic background and family factors to their performances were also identified. A ‘proficiency test’ paper was developed to investigate students’ proficiency in Mathematics, and semi-structured interviews were utilized to gather data regarding parental involvement in students’ academic activities. Several different statistical tests were employed for the data analyse. Although the findings revealed a positive correlation between students’ proficiency test score and their yearly Mathematics achievements, the relationship between students’ basic proficiency in Mathematics and their gender were not found to be significant. The students’ English language literacy was significantly related to their achievements in Mathematics. And the students’ basic proficiency in Mathematics and parents’ income was significantly correlated, but the students’ proficiency and parents’ education was not significantly correlated. Students’ English language proficiency and parental involvement in terms of emotional or financial support (such as attending private tuition class) were also determined to be the contributing factors in the students’ achievement in Mathematics.