Fresh concerns have been raised that some official investigations into the most serious cases of child abuse are still sub-standard.
One in six (16%) serious case reviews carried out in 2009/10 were found to be "inadequate", according to an Ofsted report.
Around 42% were judged to be "good" and the same proportion were found to be "adequate". None were outstanding.
Ofsted chief inspector Christine Gilbert said it was "encouraging" that fewer reviews were being judged as poor. But the report, which looked at 147 reviews conducted throughout the year, said it was "still of concern" that 23 of these were inadequate.
A serious case review should be carried out after a child dies or is seriously injured through neglect or abuse to see what lessons can be learned. The reviews are evaluated by Ofsted.
The 147 reviews conducted between April 2009 and March 2010 covered 194 children - the majority of whom were aged five or under. Some reviews covered more than one child, and 90 related to cases where children had died.
In almost two-thirds of the cases (61%) the child involved was known to children's social services at the time of the incident and 25% were subject to a child protection plan.
But the report concludes: "While this progress reflects the high level of attention that has been given to serious case reviews, nationally and by most Local Safeguarding Children Boards, it is still of concern that inspectors found 23 reviews evaluated during this period to be inadequate."
The report also found that many reviews are not being completed quickly enough. While 60 were completed in the set six-month timescale, 60 took up to 12 months, 19 took between one and two years and eight took over two years.
Ms Gilbert said: "There is a positive trend in how serious case reviews are being conducted and it is encouraging to see that more reviews are being judged good with fewer reviews inadequate. In undertaking these reviews, agencies have been able to reflect on what happened and learn from their experience. They have identified gaps in their approach and, most important, have agreed actions to improve the protection of children and so reduce the chances of such serious incidents from happening again."