The objective of the study was to assess the influence of teacher characteristics on student's academic achievements in physics in Science Technology Engineering and Mathematics (STEM) model schools in Nairobi Metropolitan region, Kenya. The study used convergent parallel mixed method design. The target population comprised 11principals, 60 teachers and 1120 students with a sample size of 368(11 principals, 39 teachers and 318 students). The study was anchored on Brunner theory. Proportionate stratified sampling and simple random sampling was used to select students while purposive sampling was used to select teachers of physics and principals. Questionnaires, document analysis guide and interview guide were used to collect data. Descriptive statistics (frequencies and percentages) were used to analyze quantitative data. Thematic and content analysis were used for qualitative data analysis. The study found out that teacher characteristics influence student's academic achievements in physics in STEM model schools. Physics performance depended on the teaching approaches and methods used by the teacher, and mastery of physics content and experience. Moreover, teachers' belief in students enable them to work harder, they encourage and motivate students to perform better in case they post poor grades. The study recommends that teachers strive to be passionate in teaching physics, believe in students' abilities to perform better in physics to work harder when they post poor grades in physics and create a friendly classroom learning environment that is favorable for learning to take place. This will ensure that teachers adopt various integrated STEM learning approaches like problem based, project based and inquiry-based learning while teaching.

The purpose of this evaluation study was to investigate the effectiveness of problem based learning as a stem learning approach in improving student's academic achievements in physics in stem model schools in Nairobi Metropolitan Region, Kenya. The evaluation used the convergent parallel mixed method design of which quantitative paradigm utilized survey design while qualitative used phenomenology approach. The target population comprised of 11principals, 60 teachers and 1120 students while 11 principal, 60 teachers and 297 students were sample size for the study. Proportionate stratified sampling and simple random sampling was used to select students while purposive sampling was used to select teachers of physics and principals. Structured questionnaires, document analysis and interview guide was used to collect data. Descriptive statistics (frequencies and percentages) was used in quantitative data analysis. Qualitative data was analyzed thematically. The study concluded that problem based learning approach is very effective in improving student's academic achievements in physics in STEM model schools in Nairobi Metropolitan region, Kenya. STEM learning approaches like problem based learning: allow physics students to work in groups, discus and share their findings with others to come up with a joint solution to a problem or task , learn through personal experiences, boost confidence among learners, assist in knowledge retention and make students to develop positive attitude towards the teachers and physics as a subject. The study recommends that the government of Kenya through the ministry of education should conduct regular training for science teachers especially the recent graduates and enlighten them in any new and emerging teaching and learning trends. Further, the study recommends that principals should come up with strategies to review school programs and time tables in order to ensure that more time is allocated to science subjects as applying problem based learning requires more than the 40 minutes according to the lessons for Kenyan system. This will ensure that teachers adopt the problem based learning approach while teaching.