Kiddo wants to study bio sciences in college. He has outstanding grades and test scores. The problem is his AP Bio teacher only does a very limited number of recommendations on a first-come first-serve basis. He has other teachers who would give great recommendations. Would it be odd to apply to a top college intending to be a bio major but no rec from the AP Bio teacher? Or are the schools more looking for character reference that could come from any thoughtful teacher?
Top schools usually ask for 1 STEM teacher, and 1 non-STEM teacher - but obviously there can be extenuating circumstances. If the Bio teacher is available, that would be #1 choice, but IMHO it is most important to have teachers that know your kid’s strengths and can communicate them in a letter. Good Luck!
So he should ask for a rec asap?
Sometimes teachers aren’t fully honest about not wanting to write for a kid, and say they are “full”. It’s easier than saying “I can’t write you a great letter”. As a teacher I say that at any balking whatsoever, find another rec.
@bopper That’s exactly the what I’ve been saying! 
Has he already asked the AP Bio teacher or was that a general statement saying that she can do limited recommendations? It it’s just that he hasn’t asked yet, I would do that ASAP. Otherwise if you think there are other teachers that can write better recommendations, ask those teachers
Some more insight… Evidently she only gives recs if you took her AP bio as a junior or senior. So you’re kind of hosed if you were an eager beaver and took it as a sophomore - which he did. Unintended consequence there. I thought I had read in the past (S1 research) that Stanford only wanted recs from teachers who taught the student as a junior or senior. Perhaps that’s where her policy comes from? Today Stanford’s policy seems to allow for more exceptions like this. He may have her again for another bio sciences course next year. If that works out then he may be able to get a rec. Too complicated! He could get great recs from a couple of non-stem teachers.
@patertrium - while it’s possible that this teacher limits numbers, or only writes for those who took APB in 11/12, etc., I really think what we’re hearing here is gentle demurrals. It would be extremely unusual for one of my colleagues to make a rule like that without exception for a kid we really wanted to write for. If the teacher doesn’t say, “I’d love to write for you and I will write a great letter and let’s meet soon to discuss” - then run quickly to another option.
In answer to your original question, however, I do think that the general field is looked at. So if DS wants to do STEM, a STEM letter would be best. A secondary letter could be from Humanities; a tertiary letter from a boss or an art teacher or coach, if applicable.
What science is your student taking this year?
Typically it is good to have academic recs from one STEM teacher and one humanities teacher. Is there another science or math teacher he could ask?
Has he actually approached the teacher? If she is unwilling because he took the class with her in sophomore year (or if prospective colleges want jr/sr year recommenders), perhaps she could make other recommendations in math/science.
He took AP Physics this year. He got a strong A in that but didn’t get to know the teacher that well. Math might be a good option. He had a high A in Calc BC and I think he has more of a relationship there. Thanks all.
Lots of bio majors will have recommendations from their AP bio teachers but far fewer will have outstanding recommendations from their Calc BC teacher. That could be an advantage. The rest of his application will no doubt speak to his love of biology while the LOR will talk about his analytical and problem solving skills.
I applied as a science major, and did not have a STEM rec. My two AP sciences were in 9/10 grade, with the AP Physics teacher retired and AP Bio taken freshman year. And then my chem teacher junior year also retired that year haha. I did reasonably well for decisions, though, and am happy with where I got in and will be attending.
If he has a good relationship with the calc teacher, I would say go for that. Since AP Bio was his soph class, I wouldnt recommend it. It’s more important that a teacher writes a good, full-page rec than what subject they teach.