The prevalence of autism/autism spectrum disorder (ASD) has been increasing across the world. Previous studies in Norway reported, that the prevalence rate for 0-10-year-old children is 1 in 166, and in the case of 11-year-old children it is 1 in 125. Moreover, another nationwide study discovered that 1 in 192 males and 1 in 695 females between the ages of 1-16 years had autism in Norway in the year 2016. This study is underpinned by the data from the National Patient Registry (NPR) for registered incidences of autism/ASD (ICD-10: F84.0 Childhood autism and F84.5 Asperger syndrome). The results show that the prevalence rates of autism/ASD in the capital city of Oslo increased from 2012 to 2016 and the number of children with autism/ASD doubled during this period. Furthermore, in 2016 the results revealed that that 1 in 349 males and 1 in 1594 females between the ages of 1-5 years old had Autism/ASD. Similarly, among the age group of 6-16 years, 1 among 157 males and 1 among 544 females had autism/ASD in the capital city of Oslo in 2016. These findings suggest a 'school-age-effect' in the increase of prevalence rates among the school-age children compared to the preschool-age children. In the following study, the results are presented and discussed along with some suggestions for the educational and healthcare authorities.