It was infiltrated by the Krillitanes, who fed the children who attended the school with chips cooked in Krillitane oil, which gave the children's intelligence a significant boost. The Krillitanes hoped to use the super-intelligent children to crack the Skasis Paradigm, which would give the Krillitanes control over the very fabric of reality. Mysterious lights in the sky, as well as a spate of mysterious illnesses and incredibly high results brought the school to the attention of Sarah Jane Smith and Mickey Smith separately. The Tenth Doctor and Rose Tyler went undercover in the school during the final stages of the Krillitane's plans, thanks to Mickey. Rose masqueraded as a dinner lady while the Doctor replaced the previous physics teacher after she somehow won the lottery despite not even playing.
The school was heavily damaged in early 2007 when K9 destroyed a vat of Krillitane oil; the oil set the Krillitanes on fire and, highly flammable itself, ignited and took a significant chunk out of the building. All the human staff were killed by the Krillitanes, and all the Krillitanes were killed in the explosion. (TV: School Reunion)
In 2008 a student of Deffry Vale High School was taking part at Combat 3000, together with Luke Smith and Clyde Langer. Clyde couldn't remember his name but knew that he was a top footballer at Deffry Vale High School. (PROSE: Warriors of Kudlak)