According to Whitfield M.D. about 90% of families are dysfunctional, dysfunctional families have a high prevalence of PTSD according to https://pmc.ncbi.nlm.nih.gov/articles/PMC9367873/ . PTSD is likely to cause children to have bad grades according to https://pmc.ncbi.nlm.nih.gov/articles/PMC7003209/ . Even a child being smacked can have an affect on grades https://www.bbc.com/news/articles/c2eyke83yz9o. Spanking causes a child to become defiant so the exact behavior you're trying to correct gets amplified according to https://www.wsbtv.com/news/trending-now/spanking-can-cause-lifelong-mental-deficiencies-in-children-new-study-says/244922240/?outputType=amp . Kind of a circular problem. Spanking has shown to alter the brain in ways similiar to severe maltreatment https://www.gse.harvard.edu/ideas/usable-knowledge/21/04/effect-spanking-brain . My solution was get rid of spanking and adopt a method that Europe is already doing. The law holds parents as authority on education, health, and daily routines but the law treats the child as an individual citizen with the same basic rights as an adult. The child has a right to a non-violent upbringing, even psychological injuries are not allowed. I am pretty sure someone was threatening death to anyone who thinks we should get rid of parental autonomy. Do people really feel that strongly about parental autonomy? To me it's the same as getting rid of smacking a dog on the nose for biting. From what I look up you might get animal abuse charges if you smack a dog on the nose for biting someone.

https://pmc.ncbi.nlm.nih.gov/articles/PMC7983058/

https://pmc.ncbi.nlm.nih.gov/articles/PMC7003209/ This study shows a direct relationship between poor academic performance and PTSD.