Okla. Admin. Code § 715:10-5-23
Qualifying out-of-state service after July 1, 1943 can be combined with Oklahoma service performed in the same school year to obtain one year of service. The combined service must total one hundred twenty (120) days of employment, excluding preschool conference, holidays or other days when the member was not required to report to work. If the Oklahoma service to be combined with out-of-state service was not as an active contributing member of TRS, the member must have worked a minimum of ninety (90) days in Oklahoma public schools. Under no condition may out-of-state service performed in one school year be combined with Oklahoma service in a different school year. Any service combined with Oklahoma service counts as one (1) year toward the maximum service allowed for out-of-state service credit.
Okla. Admin. Code § 715:10-5-23