A High Court judge concluded that "in all probability" Khyra Ishaq would not have died if there had been "an adequate initial assessment and proper adherence by the educational welfare services to its guidance".
The ruling of Mrs Justice King, made in March 2009, was released after the child's mother, who starved her seven-year-old daughter to death, was cleared of murder after prosecutors accepted her defence of diminished responsibility.
Angela Gordon, who admitted the manslaughter of Khyra two weeks ago, was formally found not guilty of murder by jurors at Birmingham Crown Court on the orders of trial judge Mr Justice Roderick Evans.
The decision by the Crown to accept Gordon's plea to the lesser charge came after she admitted five counts of child cruelty and psychiatrists agreed that she was suffering from severe depression when Khyra died in May 2008.
In her ruling of March last year, relating to care proceedings, Mrs Justice King said: "It is beyond belief that, in 2008, in a bustling, energetic and modern city like Birmingham, a child of seven was withdrawn from school and thereafter kept in squalid conditions for a period of five months before finally dying of starvation."
Mrs Justice King said schools attended by Gordon's children were voicing their concerns, "in particular their concerns relating to their belief that the children were not being fed properly".
She said: "The schools did all they could to bring their concerns to the attention of the relevant authorities.
"These concerns were not taken sufficiently seriously and were not adequately investigated."
Social services' attention was drawn to the family the day after the mother withdrew them.
Between then, December 2007, and Khyra's death in May 2008 the police had one glimpse of her.
The judge said: "No professional person, whether teacher or social worker, saw the children after February 2008 and no-one tried to see them."
Mrs Justice King said Khyra's death "was caused by and is the responsibility of her mother" and her partner.
However, she added "but on the evidence before the court I can only conclude that in all probability had there been an adequate initial assessment and proper adherence by the educational welfare services to its guidance, K would not have died".