We bought our daughter a ball python at 7 just before her 8th birthday. She asked for it as her gift and it was the first snake our family ever had. She had experience caring for our dog and had been equestrian riding since 4 so we felt she was responsible and respectful enough with animals. Our 5 year old son subsequently asked for his own ball python a couple months later for Christmas.
Between the two my daughter has been more responsible and my son needs to be monitored. Both must ask for permission before taking the snakes out and sometimes are told no. Both still tend to not close the cages properly so we follow through with that as well.
Overall, it has been very positive.