You have made a captivating argument I wish to agree with for a relative who passionately wants to assist a brother man will want to extend the help regardless the child still lives with the biological parent. On the contrary to your compelling position I'm having it on a different thought that this approach of sending the child fees to the parent will not last long relative to when the child living with the relative. And this is not only about paying the child school fees but taking care of the whole well-being beyond her school fees which is part of the burden bore by the parent.
In my tradition, it is also expected that the child you are taking care of will also assist you at home with simple domestic work. I am not talking about slavery but the relative will be more committed to covering the child's expenses if he is in his house. I wouldn't mind sending my child to live with a relative but such a person would be special. I have a brother-in-law I know would be a better father than I. Some children are also good to be sent to a boarding house or live with a relative because of their behavior. However, it is ideal for parents to raise their children.