From where I stand , I am not in favor of encouraging kids with cash just because they have got good marks .
My parents used to encourage me like this. Whenever I made progress in studies , they bought me my favorite books ,which not only motivated me to learn ,but also helped me get along well with my studies.
To get kids motivated to learn , I think we should not treat every child in the same way. To some students , oral praise is essential . Don’t save the praise for only the top score. If possible, involved other adults in praising them . However, this method may not work well with other kids. Maybe what is more important to them is to water a movie or go on a trip together with their parents . It just depends.