Research reported in Family Relations by Lisa Strohschien (University of Alberta) challenges the notion that parenting practices diminish after divorce. In a large longitudinal study Dr. Strohschien found that divorce did not change parenting behavior for most parents.
The study used data from the National Longitudinal Survey of Children and Youth (NSLCY) to compare the 208 families that divorced between data collection points to the 4,796 households that remained intact. The study compared nurturing, consistent and punitive parenting between the households.
The findings suggested that most parents maintained very stable parenting practices, and it was only a few parents who were overwhelmed, unable to cope, and became less nurturing, inconsistent, and punitive.
These results are extremely important because for years family courts have poured money into mandatory parenting classes for divorcing parents (called things like "putting children first"), when in fact, most parents do not need the classes. The parents that may be unable to parent consistently are the parents who need the support, but these results suggest they are the minority.
I would suggest that a post-divorce interview with the children would help identify the parents who need the support, as children are very capable of reporting what they need after divorce, and are conscious of when a parent is punitive and no longer invested in their well-being.