Performance in Mathematics in Meru County, Kenya from 2012 to 2016 has consistently been deteriorating. The purpose of this study was an evaluation of how the administrative strategies designed by the principals affected students’ performance in the Kenya Certificate of Secondary Education (KCSE) in Meru County. Objectives that directed the study were to evaluate the various attributes on student performance in KCSE examination in Meru County. The objective was to evaluate principal’s support to teachers through Mathematics seminars/workshops and student’s performance in Mathematics. This study used ex post facto design. The research instrument was Mathematics teachers’ questionnaire, KCSE document analysis for five years in Meru County and Principal’s interview guide. The target population was 299 principals and 836 Mathematics teachers in the County. This study used stratified random sampling with proportional allocation. The sample size was 30% of the total target population translating to 92 principals and 251 Mathematics teachers. Validity was ensured by piloting the instrument. Reliability was ensured by using split half technique. The findings revealed that principals were not sponsoring Mathematics teachers to attend workshops and seminars. The principals cited a lack of resources and budgetary allocation to the low number of Mathematics teachers attending seminars and workshops. The findings of the study were expected to be useful to the Ministry of Education, teachers and students as well as other stakeholders in the education sector.