You can check your child's assessment number from your former school's head teacher. If the head of school is not willing to provide or has no idea what to do, then visit the sub-county director of education.
The head of school can view the assessment number by login in to https://cba.knec.ac.ke.
Below is a pdf that provides a step-by-step guide on how to check the assessment number.
To view or download pdf file login or register for free.