Take pre-calc in 11th, and then take BC as a senior.
You receive an ab "sub-score" when you take the bc test, as about 60% of the bc test is ab material. And it's certainly possible to learn of the material for the bc test in one year.
However, if the bc class offered at your school assumes you've already taken ab, you may want to do some self-studying/summer studying to catch up, as the class may start with bc material that requires ab knowledge.
Read here: http://apcentral.collegeboard.com/ap...escription.pdf
about the sub-score for more info.