Can a father blood type B and mother blood type O have a child who is blood type A?

According to two different web sites that I looked at, no. With that combination the blood type of the child would be B or O.

http://www.biology.arizona.edu/human_bio/problem_sets/blood_types/inherited.html

http://www.dnatesting.com/resources/blood-type-paternity-test.php

There are sub groups to blood typing, and without knowing a complete blood work up, it is not really possible to say with the limited info you have provided.

If there is doubt of the father of a child, please have a DNA test done.