Simplify the following text for a Grade 9 native English-speaking person.
Original: He attended Mayville Preparatory School , Southsea from 1912 to 1915 and then Portsmouth Grammar School from 1915 to 1924 , where he showed no particular academic aptitude but very much enjoyed the Officers ' Training Corps ; when in later life he returned to present prizes , he told the pupils that his parents would have been very surprised to see him in the hall on speech day because he had never come close to winning any school award .
Simplified: He went to school in Southsea from 1912 to 1915 and then Portsmouth Grammar School from 1915 to 1924 . He was not very good at school , but liked the Officers ' Training Corps ; later he returned to present prizes and told the pupils that his parents would have been very surprised to see him in the hall on speech day because he had never come close to winning any school award .