The aim of this study was to investigate the test results of reading speed, reading comprehension, word comprehension, spelling, basic arithmetic skills, and number sense (intuitive understanding of numbers) by children treated for brain tumors. This is a retrospective study based on medical records, including standardized academic tests. In the years of 2010 to 2014, all children in the area of Stockholm between 7 and 18 years (IQ <70) who had no major linguistic or motor difficulties after they had undergone treatment for brain tumors were offered a special education assessment one year after treatment, at school start, or the year before a transition from one stage to another. Our results indicate that children treated for a brain tumor are at risk of having difficulties in spelling, reading speed, and arithmetic and that the test performance may decline over years in arithmetic and spelling. Children diagnosed at age 0 to 6 years may need extra tutoring at school start, especially in basic arithmetic skills. In both reading and mathematics, many children perform better on tests focused on understanding than on tests focused on speed. Continuous special needs assessments including different aspects of literacy and numeracy, are important for understanding each child's specific needs.