Slater's mother, Rachel Peacock, who had been living with Morgan for two months, was cleared of causing or allowing her son's death, but was given a 12-month community order after being convicted of a cruelty charge.
Officials say 80 local authority areas met the interim thresholds (of 21 months from entering care to adoption and matching a child to a family within seven months of a court orderbeing made), but 72 did not meet one or both of these.