Annals of Landmark Events
Right from the onset the School had been set for glory and molded for greatness and monumental achievements were recorded thereonÂÂÂ
1943
- Establishment of Offa Community Grammar School - by Offa Descendants Union ( making it the oldest Community Secondary School in the then Northern Nigeria, and the first full-fledged Secondary School in the then Ilorin Province). Later named "Offa Grammar School" (O.G.S. for short).
- Appointment of Mr. Solomon O. Ajayi - (a prodigious and enthusiastic teacher and Zonal Secretary of N.U.T) as the pioneer Principal.
- Accommodation of the new school (OGS) within the premises of Iyeru Okin African Church, Offa.
- Acquisition of the permanent site for the school through the personal efforts of the then reigning Oba - Oba Wuraola Isioye - a man of vision and proven integrity.
- Appointment of Rev. R. N. Ludlow as the first chairman of the Board of Governors. Other members being Mr. J. A. Oyeleke. Mr. J. O. S. Onawola, Mr. John Oyediran, Alhaji Sanni Giwa, Alhaji Gbadamosi Ijaiya, Mr. Samuel Adesiyun, Alhaji Bello Jatto, Mr. John Opaleke, Alhaji Aliu Olatinwo and Mr. I. David Ogunwumi - they all gave their all to ensure that OGS was put on a sound footing.
- Admission of the foundation students - Johnson Adegoke, Bamidele Fafemi, Olagunju Kolawole, Olarinoye Omirinde, Olagunju Ajiboye, Salami Olatunde, Saliu Olatunde, Albert Adetoro, Jimoh Oyawoye, Joseph Asa, Godwin Johnson, Emmanuel Jenyo, Samuel Ogunsola, Samuel Odewale, Jacob Banwo, Mustapha Awoyemi, Muritala Olatunde & Peter Alabi.
- Late Mr. J. A. Oyeleke (a famous Headmaster) suggested what became the school motto - LABOR OMNIA VINCIT (Latin), meaning PERSEVERANCE OVERCOMES EVERYTHING.
1944
- Construction of structures at the permanent site began - part of the U-shaped building (the popular Assembly Quadrangle). It is the oldest building in O.G.S.
1945
- Appointment of Rev. J. B. Olafimihan - a disciplinarian and one of the prominent members of Offa Descendants Union - as the new Principal. He was nicknamed "Jacob" (i.e. Janitor, give me a branch of Casia) for flogging erring students no matter who their parents were.
- More students were admitted into OGS from Offa and its environs - Ijagbo, Ipee, Igosun and Erin-Ile etc.
1946
- The Thornsburn Upgrading Inspection Exercise took place. An outstanding success was recorded.(Footnote - Mr. Thornsburn was a British Education Official assigned to inspect the School with the purpose of terminating its existence or encouraging it.)
- Staging of the first Inter-house Sports Athletics Competition.
- Movement of the School from the Iyeru-Okin African Church premises to its permanent site in the adjourning plot.
- The first set of OGS students graduated after obtaining Government Class IV Certificates (or Junior Cambridge School Certificate). Some OGS Students proceeded to older schools where they completed their secondary education. A clear example was Mr. Jimoh Oyawoye (now Professor M. O Oyawoye)
- Mr. S. O. Ajayi (Foundation Principal) left OGS for United Kingdom.
1949
- Change of personnel as Late Pa JA. Osanyin (perhaps the first University Graduate from Ijebu-Jesha) took over as Principal from Late Rev. J. B. Olafimihan.
- Passing with flying colours of the Upgrading Inspection (the second one) which resulted in the School having students in Secondary Class Five for the first time in January 1950.
1950
- OGS began to receive grants from the Regional Government of Northern Nigeria (Kaduna) for payment of staff salaries and construction of some permanent structures.
- Institution of the OGS scholarship scheme to encourage or assist the best students from Offa or its environs. It was later extended to students from outside Offa. Early beneficiaries of such scholarship awards were Mr. E. O. Onifade, Mr. S. A. Adebiyi etc and later non-Offa Indigene Student - Prince D. A. O. Abegunde.
1951
- Entering of seven OGS Students for the Last London Matriculation Examinations held in Nigeria (June 1951).
-  Registering of the first set of students of OGS for the Senior Cambridge School Certificate Examinations at the Ilesha Centre (Dec. 1951).
- The following students were registered for (b) above - Adebiyi S. A, Adekanola  P. A., Adetoyinbo G. A., Afolayan E. O., Ajagbe E. O., Alalade O.I., Bede S. O., Dare J. K., Esan J. A., Fadiji I. A., Gbalajobi O. A., Okobi C. E., Olukanmi L O., Onifade E. O., Oyeleke Y. A., Oyelola J. A., Oyeyemi Y. F., Oyewole S. O., Sofoluwe F. O., and Tolani N. D.
- Mr. Yunusa Folorunsho Oyeyemi (now a man of mark in school and Public Administration) obtained Division One in (b) above.
1952
- Mr. Oyawoye S. O. (now a renowned Medical Doctor) passed his senior Cambridge School Certificate Examinations in Form 5 (instead of 6, that is a year earlier) - evidence of J. A. Osanyin's policy encouraging brilliant students.
1954
- Movement of Boarding House from rented quarters in the town to its permanent structures in the OGS compound.
1955
- Replacement of plank beds with Iron ones
1956
- With the School recording 100% success in West African School Certificate Examinations more grants were provided by the Govt to the envy of other schools in the North. The list of the students who performed such a scholastic feat include W.O Nasiru (who led the class with aggregate 10 thereby setting an academic record that took 16 years to shatter), Ademuyiwa A. Adeyokun, Ayantayo Ayandele, Emmanuel A. Olagoke, Hamzat O. Ijaiya, Adeyemi I. Jatto, Solomon A. Otegbola, John O. Olowokure, Olarinoye Ogungboye, Micheal O. Olaitan, Emmanuel S. Ajayi, Benjamin B. Elesin, David A. Oyedokun, Isaiah A. Bilewu, Daniel B. Aloba, Sunday O. Kuponson, Muibi M. Adedosu, Samuel D. Ojo, John O. Adegbile, Ephraim O. Oguntona, Adebayo O. Osanyin, Oladele Olashore
- The building of Science Laboratories - Biology, Chemistry and thearrival ofMr. Marshall - the legendary General Science Master.
- Introduction of General Science in the school curricula
- The Premier of the Northern Region, Alh. Amadu Bello, paid a courtesy visit to the school.
1958
- End of 6-year Secondary Education Programme in O.G. S. Forms 5 and6 students sat for the same West African School Certificate Examinations.
- A small Hall named OYELEKE HALL (after late Mr. J. A. Oyeleke) was officially commissioned by the smallest boy in form one - Samuel Bisi Abikoye.
1959
- Late Mr. Fortunatus O. Shofoluwe founded the Offa Grammar School Old Boys Association (later Offa Grammar School Old Students' Association) thus becoming the foundation National President of OGSOSA.
- Students-versus-students riot erupted in the school involving final year students. It affected negatively the performance of the set in WASCE.
1960
- Mr. Y. F. Oyeyemi (1951 set) was appointed the Vice - principal of O.G.S., the first old student to be so appointed.
- Minor riot broke out over the quality of bread being supplied by Alafia Bakery, Offa to the School .
- Nigeria's Independence from colonial rule was celebrated with great fanfare.
1961
- The great architect of OGSOSA, Mr. F.O Shofoluwe, was lost to death.
- Admission of female students into Offa Grammar School; they were Mulikat Oyebode, Ayoola Adevemi, Cathrine Ogunoye (a great Athlete), Shade Balogun, Mulikat Lawal, Musili Ajeigbe, Tope Shonowo, Funmilayo Fafemi, Josephine Fakeye, Deborah Gabriel, Ibidun Osanyintolu, Rachel Adetumobi and Sona Briggs. Footnote - This marked the beginning of co-education in OGS.
1962
- Rev. R. N Ludlow - a long-lasting friend of OGS - paid a flying visit to the School and took group photograph with the members of the house named after him (Mr. Odeniyi Moses was the House Captain).
- O.G.S won the zonal trophy for coming first in 9 of the 15 events in the zonal Athletics meet (South West Zone).
1963
- Mr. Olu Aderemi Fatoke became the Northern Secondary Schools' High Jump champion after clearing over six feet (Kaduna 1963).