Inspectors have rated Doncaster Council's support for local schools 'ineffective', finding 'a pressing need' for improvements to regional strategies.
Analysis of the council's arrangements for supporting primary and secondary schools by Ofsted found local systems for collecting and analysing school performance data were 'not fit for purpose'.
A report following the five-day inspection found council school improvement services had failed to keep formal records of how governors manage and support schools. Inspectors added that Doncaster was not using its powers to intervene in failing schools 'in a consistent way'.
More than half of pupils in the borough attend a school that is inadequate or requires improvement.
Responding to the report, Cllr Nuala Fennelly, cabinet member for children's services, education and skills, said 'Although the conclusion of the inspectors was that we clearly are not yet in the shape we want to be, we have achieved a lot in a short space of time and from a relatively low base in terms of adequate support.
'This is an honest appraisal of where we are and we welcome that.'
'I am under no illusions that we have some considerable progress to make and we will do. We are determined and that determination is shared by schools and partners,' Cllr Fennelly added.
