Explain your premise for WHY redistribution of wealth is acceptable.
You explain why it is unacceptable. Surely, we start off by assuming something is acceptable. If you want to say it is not acceptable, you need to provide reasons to show this.
explain why that premise can't be applied to redistribution of health
Everyone has a right to health. Therefore it is wrong to actively harm someone's health. Removal of a kidney has undeniable health risks and so by forcefully removing a kidney from someone you are violating their right to health. I also believe people have a right of control over their own body. You are obviously violating this right if you remove one of their organs without permission. The person with no kidneys is in poor health and so attempts should be made to correct this but this can't violate another person's rights. If a person decides to donate a kidney then that is their choice and is ok, although it is preferable to take kidneys from people who no longer need them - the dead.
kicking intelligent kids out of classrooms so that we can dedicate more time to the slower ones
This is violating the right of education of these 'intelligent kids' and is therefore wrong. The 'slower' and 'intelligent' kids both have the right to education and they should both be provided for.