A teaching assistant at a Hatch End High School was arrested by child abuse officers this week after allegations of assault.
Police have confirmed that a member of staff at Hatch End High School has been bailed until April following his arrest, while the school told the Harrow Observer he has already been sacked.
Allan Jones, headteacher at the school in Headstone Lane, said: "The school has recently terminated the contract of a member of staff for breach of duty of care.
"He is no longer at the school and the relevant authorities are now dealing with it."
Breach of duty of care is listed legally as negligence or harm to another individual.
Vish Patel, spokeswoman for Hendon police who are overseeing the investigation, added: "Officers from the child abuse investigation team at Edgware are investigating allegations of assault.
"A 28-year-old male teaching assistant was arrested and bailed until April pending further investigations."
Councillor Lurline Champagnie (Conservative), who is a governor at the school, agreed it was up to the school and authorities to deal with the issue, and not governors.
But she added: "All I can say is that in such circumstances it is always difficult, and it’s very unfortunate.
"But this kind of thing is not in the hands of governors and the school will be acting as they see appropriate."
The mixed school in Hatch End has nearly 1,500 students on its register ranging from 12-19 years old and was one of the first in Harrow to start up a sixth form in partnership with Harrow Collegiate in 2006.
In its latest Ofsted report, three years ago, Hatch End High was recognised as ‘good’.
However, it received the borough’s third lowest A*-C GCSE pass rates (including English and maths) in the latest results released two weeks ago.
Former pupils at the school include Life On Mars star Philip Glenister, who played the part of DCI Gene Hunt in the cult BBC series.