I think it must be demoralising for a child to be stuck on bottom table. They caught in a cycle of low expectations with no chance ever to try the harder work. Sometimes people assume a child on bottom table is stupid and the child can come to believe that they are stupid.
Consversely think that that some of the brighter children on the top table can become swollen headed and believe that there is no need for them to work. This happened to my son who has had a huge culture shock when he is not in any of the top sets at secondary.
Surely there must be a better way of managing differentiation, so that children are unaware of where they are in the class. I believe that Finland doesn't have top or bottom tables. It would be interesting to know how Finland manage to stretch the brightest children and support the weakest.