A judge has criticised school authorities for not taking complaints about a perverted music teacher seriously.
Michael Crombie was allowed to molest 16 girls at two schools over 30 years unchallenged, the Old Bailey heard on Friday.
Judge Wendy Joseph said: "It is clear complaints were made to the school by a number of the girls on a number of occasions but no one took adequate steps to stop this defendant preying on these girls."
The offending came to the attention of police after they began investigating Crombie when he retired and started molesting students he was giving private lessons to.
Michael Crombie, 75, pleaded guilty last month to 47 counts of indecent assault between 1964 and 1993 at Beal Grammar School and Wanstead High School, both in east London.
He also admitted two of sexual activity with a child between 2005 and 2007.
Crombie, formerly of Woodford Green, east London, was jailed in 2010 for the private lessons assaults.
The seven-year sentence was reduced on appeal to five years and he had been due for release in May.
Judge Wendy Joseph jailed him for a further three years, saying she had to use sentencing legislation for the time.
But she added that the victims had been affected by the "turmoil of abuse" they had suffered.
The judge said it was Crombie's "denials and intimidation" which had prevented the matters coming to light sooner.
She had read nine impact statements and a common element was that Crombie "took over their lives and effectively seduced what were innocent and trusting girls".
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