The present study is divided into two parts. The first part examines the performance of Lebanese students in public and private schools in Lebanon in 8th grade using the TIMSS 2007 data. The effects of students’ dispositions and teacher characteristics on the performance of students in public and private schools are also studied. Results indicate that private school students in Lebanon perform better than public schools students in each mathematics content and cognitive domain in TIMSS 2007. Having a positive affect towards mathematics is positively related to students’ achievement in both public and private schools. Self-confidence has a positive relationship to students’ achievement too in public and private schools; and the relationship is stronger in private schools. Most of the teacher characteristics have little or no relationship to students’ achievement except for teachers’ age and teachers’ gender. On average, students with older teachers and female teachers usually perform better. The second study examines the mathematics performance in TIMSS 2007 of 8th grade students in seven Arab countries: Bahrain, Egypt, Jordan, Lebanon, Saudi Arabia, Syria, and Tunisia. The effects of positive affect towards mathematics, valuing mathematics, self-confidence in learning mathematics and some teacher characteristics on mathematics achievement are studied for each country. The results show that Data & Chance and Number are two mathematics content areas in which most of the seven countries have weaknesses. Some of the countries performed better in Reasoning than in Knowing or Applying. In all the countries, positive affect towards mathematics, valuing mathematics, and self-confidence were positively related to students’ mathematics performance. Neither teacher age, years of experience, degree, nor certification had any noteworthy relationship with students’ achievement in all seven countries. Students with female teachers scored better than students with male teachers in Bahrain and Lebanon. In the other countries, students with female teachers and students with male teachers had similar performances. Policy makers should find ways to increase students’ positive affect towards mathematics, how much students value mathematics, and students’ self-confidence in learning mathematics.