That's definitely been a concern that has been raised in the UK. The need to set up the appropriate design and selection process is key. The rigour that you have to bring to the design is paramount to addressing some of the equity questions that you raised. So different approaches, like random control trials, other social science techniques, can be used to avoid this problem of “creaming” and other things.
It's the same kind of issue that you see elsewhere when there's testing, for instance, of pharmaceuticals. These are appropriate, ethical questions to raise. They're very much at the forefront of the design.
That's why it's important, as well, to have appropriate evaluation, to have a third party evaluate these projects.