I do wonder if there is any chance that the reason that there is a spike in reports of abuse on the Saturday following report cards coming out on a Friday is because it is more likely to be reported?

It's not mentioned anywhere in the article, but if someone said to me that 2 things are true: 1. There is some correlation between report cards being returned and child abuse 2. There is a spike in reports of abuse on Saturdays when report cards are returned on Friday

I wouldn't immediately think "cool, lets return report cards earlier. Problem solved"

Other than not really solving the problem of abusive parents, this also doesn't actually rule out child abuse happening accross the board but not being reported on weekdays.