Diagnostic Achievement test Construction for schools and colleges provides a comprehensive and concise foundation to development of Agricultural science test items for senior secondary schools in Nigeria. It explains, with lucidity the techniques of constructing and validating a diagnostic achievement test with good psychometric properties in line with Item response theory. The research work is presented as a practical activity to measure the cognitive, affective and psycho motor domains of students in Taraba state of Nigeria. The research work is recommended to all students and teachers of Education in particular, to everyone who has interest in assessment of students.