But during a monitoring visit in March the inspectorate found that children at risk of immediate harm are now responded to swiftly. Thresholds for intervening are also "well embedded and applied consistently in most cases", says Ofsted in a letter to the council.
This latest visit looked specifically at the work of the assessment and intervention and family support and protection teams.
Inspectors say that the quality of social worker assessments of cases has significantly improved, which is leading to better planning of how children can best be supported.
The use of regular multi-agency reviews of children in need cases is particularly praised.
"This is a huge improvement; previously these children's needs were not prioritised or reviewed, leaving many of them in harmful situations for lengthy periods of time," states Ofsted's letter.
Efforts to tackle knife crime also impressed inspectors. They found that children's services is working well with partners across the borough to ensure young people, who are the victims and perpetrators of knife attacks, are kept safe.
The department's leadership is also praised for a commitment to continuous improvement and for supporting staff with training and professional development opportunities. This is helping to reduce staff turnover, reduce caseloads and give social workers time to build strong relationships with children.
"This approach has created an environment in which social workers feel listened to and supported to develop their skills and knowledge," states Ofsted's letter.
"Staff enjoy working in Tower Hamlets and more agency social workers are applying for permanent positions."
This is the sixth and final monitoring visit by Ofsted ahead of a full inspection in the autumn.
Inspectors have warned Tower Hamlets that further improvements are needed. They found that while social workers are regularly supervised there is a lack of clarity from managers about improvements needed.
"Not all practice is routinely analysed by managers to ensure that work is making a sustained difference to vulnerable children's lived experiences," says Ofsted's letter.
Ofsted also wants to see consistent practice in helping neglected children, some of whom have been known to a number of services for a number of years.
Tower Hamlets mayor John Biggs said: "I take encouragement that Ofsted inspectors found further improvements in the level of care and planning for our most vulnerable children.
"We have set a high bar to move from an inadequate rating to good in just over two years. There is work to do and we will maintain a relentless focus on what Ofsted have advised in order to be ready for our full inspection this autumn."