I think you need to define what you mean by "excellent." At many schools—SLACs usually—excellence is defined by things like doing research with undergraduates (which is a common practice at those schools).
I'm a tenured prof at a flagship research 1 university, in what would usually be called an "excellent" department (top 10 doctoral program, high faculty research productivity, etc.). But I virtually never do research with undergrads. I never get to know them outside the classroom. (And in my case, it's not that I don't want to. It's that my job isn't structured to facilitate or reward that kind of interaction.)
My younger sister, however, did her undergrad at Knox College in Galesburg, IL. It's a quality little SLAC with an important role in history (one of the places that Lincoln and Douglas debated), but its current faculty aren't typically leaders in their fields. Still, my sister spent a summer doing funded research for a chemistry prof. She was doing computational chemistry calculating some sort of outer atmosphere reactions. Her prof wasn't a leader in her field, but she was surely a capable researcher with an interesting project going on, and the school had structures in place to encourage faculty/student research collaboration.
So, unless your kid is some sort of prodigy whose intellect will only be challenged by working with the brightest professors in her field, I don't think you need to focus on the most "excellent" biology or physics department. If research opportunities for undergrads are what matter to you, then you should be looking for colleges that encourage and reward those sorts of experiences, which tend to be the SLACs. Find a few SLACs that fit your kid well, make sure they encourage undergraduate research, make sure their bio and physics departments are reasonably capable, and I think you've got a good match.
And FWIW, I do graduate admissions for my department, and we're in the process of reading applications right now. I am *always* more impressed by a student who has done extensive independent research under the supervision of a lesser-known faculty member at a SLAC versus a student who took some large lecture classes with one of the "stars" in my field at a big research university. So, if your kid may ultimately be grad school bound, I think the quality of the research experience is more important than the pedigree of the program. But I know that others might disagree with that thinking.
The only exception to this line of thinking is if your kid wants to do some sort of research that requires really sophisticated equipment that a SLAC is unlikely to have. But there's plenty of important work to do in biology and physics without multimillion dollar labs.
This poster is spot on.
Thank you for your post. I said 'excellent' because I did not want to focus on "best". Perhaps 'decent' would have been a better description. I am not really looking for a liberal arts school, more of a science and math (not really engineering) school that is small and east of the Mississippi. With the exception of Rose Hulman, I haven't been able to find one. The student in question is math and science oriented and fairly exceptionally so, however the student would have to have a waiver for any foreign language as he has a language based LD. The LD makes English and history classes time consuming when he would rather be in a math and science class. So, he would like to limit those. The student is introverted and a smaller campus and student life is more appealing. The student has been leaning more towards physics lately, as a result, that is a higher concern. At this point, he is planning on getting a PhD regardless.
Slightly O/T, but something to consider, OP, is looking for a school that has a strong office of disability support as well as a strong math/science program. Most colleges have distribution requirements (required for accreditation) that include general education courses that he might not be able to get a waiver for. In other words, it's hard to get an undergraduate degree from an accredited college without English or history classes. Foreign language requirements are a little different. That said, colleges can provide 504 accommodations for a student with a documented LD, so he can get support if you find a school with a good support office. Just something else to consider in your search.
Sorry for the temporary threadjack.