Birmingham Children's Trust was launched in April to improve standards within the council's children's services department, which have been rated as "inadequate" since 2009.
But in the second monitoring visit since the trust took over provision, inspectors found that in some neglect cases social workers are over-optimistic about the welfare of the child, which is preventing swift decisions being made around further intervention.
Concerns also remain around the evaluation of social work practice. While a new evaluation process has been set up inspectors say that more work is required to ensure the trust can effectively measure performance and learn from its findings.
In addition, the trust's work with partners was found to not always be consistent, and they are not always actively involved in multi-agency child protection meetings.
"The trust is continuing to make some progress in improving services for its children and young people," states Ofsted in a letter to the trust.
"However, a number of areas continue to require improvements in services for children and their families. These include the quality of the trust's evaluation of social work practice, the consistent engagement of partners in contributing to multi-agency meetings and ensuring that in cases of neglect, over-optimism does not lead to inaction."
Social workers' communication with parents was also deemed to require improvement. Inspectors said the language being used to explain decisions "can still be complicated and difficult for some parents and older children to understand".
Despite the concerns, inspectors found that no children were found to be at risk of harm and there were no major delays in the progress of cases.
Meanwhile, thresholds for support were found to be appropriate and in most cases delivered swiftly. And social workers were found to know their cases well, with children regularly seen alone and their views recorded through "age-sensitive direct work".
Birmingham Children's Trust chief executive Andy Couldrick said: "We are encouraged to see that Ofsted is continuing to acknowledge that progress is being made, in this case with services we offer to young people leaving care and in long-term care.
"As a trust we benefit from having one focus - that of improving outcomes for our children, young people and families. We acknowledge there is still work to do, but we are seeing tangible evidence of improvements after every Ofsted visit and I want to thank our staff for their continued hard work."
Ofsted's first monitoring visit since the trust took over children's services took place in May and found good progress in improving support for care leavers. Inspectors were particularly impressed by the setting up of a specialist leaving care team to support unaccompanied asylum-seeking young people.