John Eames, 44, who appeared in court with his head heavily bandaged after being beaten and left covered in blood by inmates at Brixton Prison, looked shaken as he heard his sentence.
Parents of the victims - the children have suffered sleeplessness and loss of confidence since the attacks - gasped and clutched each other as the judge jailed Eames, of Dagenham, east London, for his 'very grave breach of trust'.
Eames committed the offences while working at a temporary job he was able to obtain despite having a 20-year-old conviction for exposing himself.
He was found guilty on Monday of five charges of committing acts of gross indecency with or towards a child under 14 years of age. Judge Geoffrey Rivlin QC told Eames, who is married, that he had committed 'appalling' indecency.
Eames's conduct was 'distressing and revolting' and had a 'profound' effect on his young victims, although it was to be hoped they would eventually recover, the judge said.
Eames claimed in court that the oldest of the girls invented her account and made smaller children go along with it because he once accidentally struck her.
He appeared with a bandage covering part of his head and his right eye. His counsel, Linda Stern QC, said he was beaten after being put in a room full of other prisoners before being taken to court.
She said that in many ways Eames was immature, and in view of the offences of which he was convicted would find prison life an ordeal.Reuse content