The effect "could be large". Do you have any data to support this?

Some forms of coaching "add over 100". Do you have data to support this?

Poor black/hispanic kids don't have test prep programs in school. So they are unable to get privately provided test prep or have no incentive to do so, and therefore receive a smaller amount of test prep than other racial groups. Do you have any data to support this?

The effects of a superior school "could be large". Do you have any data to support this?

You also say that you learned a lot from black and hispanic pupils. Would you have learned less from white pupils?