The first phase is the Junior Secondary (JS) level when English language, Mathematics, Integrated Science, Introductory Technology, Agricultural Science, Social studies, Computer Science, Nigerian languages, Religious studies among others are taught to all students.

At the end of phase one, students must pass an examination conducted by the National Examination Council (NECO) before proceeding to the Senior Secondary level. At this phase, students are allowed to offer subjects according to their aptitude and relevance to their career choice. On completion of the level, they become eligible to sit the Secondary Schools leaving examinations, SSCE and WASCE respectively conducted by NECO and West African Examination Council (WAEC), and the Joint Matriculation Board Examinations (JAME) for the universities, polytechnics and colleges of education.

Students Population as at July 2002 was 2044 with 889 being females and 1155 being males. There are 6 classes with 36 streams. The disposition into the classes is as in the table below.

The school has been performing brilliantly in the various local and state educational contests and national examinations. Students have also shown scholarship in local, state and national educational competitions and have won many awards.

The proprietor of OGS is Offa Descendants Union.