The main purpose of the study was to assess teachers' and students' perception of gendering process over girls and boys at secondary schools. Specifically the study aimed at examining the impact of socialization to the students' academic performance in secondary schools. A total of 182 respondents were interviewed by the use of semi structured questionnaires, Focus Group Discussion and direct observations were employed to obtain the required information. Results show that the common gender stereotypes in secondary schools include "boys are intelligent", "boys prefer studying science subjects", "girls prefer studying art subjects", and "girls are inferior". Results reveal that socialization process promotes effective learning and teaching, increases cooperation and participation, improves students' performance and promotes school ethics conformity. The study concludes that Gender – aware and - sensitive teachers and students play a vital role in promoting gender equality and in turn will interact in a gender lens with the society they are born into. The existing negative stereotyping notions and prejudices amongst students and teachers over girl students; call for re-thinking of the current Tanzanian Women and Gender and Development policy to address negative assumptions and prejudices over girls.