Age Adjusted Incidence Rates Using Poisson Regression


I am not sure how to calculate age-adjusted incidence rates using poisson regression. I am comparing injuries for children at two schools, offset by child-days in school and would like to adjust for age. I ran the following model:
poisson injuries school i.age, offset(childdays)

I am able to determine age specific incidence rates and an age adjusted incidence rate ratio but don't know how to calculate an age adjusted incidence rate for the two schools.