I think they can perform just as well as anyone, first because the ToE is usually a small portion of the biology class even in public schools, and second because a kid can learn the mechanism of RM+NS without necessarily believing that it can amount to anything. (of course, this last one depends on if the parents don't think evolution is the devil, which it isn't)
And, if you ever remember your biology classes, you don't really need to believe in evolution to know how a cell works, or how dna is being transcripted, etc.
I take a different view on these things. What I always wonder about is all of the great future biologists that were scared away from science by homeschooling. I will agree that one does not need to understand evolution that well in order to score well on high school standardized tests. I think this speaks more to the awful state of standardized tests and high school education as a whole, but that is a topic for another day. So even if kids are not taught evolution and pass tests with high marks it still does not change the fact that parents have told their kids that the evolution boogey man is lurking out there in biology classes. This boogey man can lead you to atheism and a rejection of God if you let him get his fingers into you. What else is a kid supposed to think other than to stay away from further education in the biological sciences? How many great future scientists have been scared away from a great and rewarding career because their parents threatened their everlasting soul with damnation if they did so?
Also, one of the philosophical tenets of science is that there are no sacred cows. There are no questions that should not be asked, or hypotheses that should not be considered. From the time of Galileo science has given the religious aristocracy the middle finger time after time. IMHO, science should have an air of being crass, anti-establshment, and daring. This shouldn't be taken too far, don't get me wrong. However, science doesn't work if it is kowtowing to unsupported religious beliefs. Learning science should be a slap in the face. It should open your eyes and tell you that whatever you believe is wrong, and this is why.
I'll leave it there, but there is plenty more to the rant if you want to hear it.