Principal Willie Kuria said the consistently good performance is not by sheer luck.
The school, he said, lays strategies and sets a target at the beginning of each year to guide both teachers and students.
Further, the school appoints a principal who is in charge of Form 4, helping handle all matters concerning the candidates.
"We ensure there is maximum discipline. Our boys are quite disciplined, and we are grateful for that," Kuria said.
"We are also very prayerful and work as a team. Teachers, students, the board, and parents all work together for the desired goal," he added.
Kuria said the school is proud to produce excellent candidates each year despite having a large population of learners.
The school has about 2,000 students, with each class having up to six streams.
The school hit a 10.59 mean score in 2013, followed by 10.73 in 2014 and 10.74, the highest ever, in 2015, with the lowest score being 8.47 in 2018.
"Since then, the school has been working towards living to the expectations of the status we have set," Kuria who is also the chairperson of the Kenya Secondary Schools Heads Association, said.