Bachelor of Computer Applications (BCA) is for students who are interested in computer science and IT. Though mathematics in 12th grade is required by some universities, most welcome students from arts and commerce streams. The course includes programming, databases, and networking, so students without a science background can join.
But having a science background can be helpful, as courses such as algorithms and data structures are based on logical reasoning. If you do not have a science background but are very interested in technology, you can still do well in BCA with hard work. Some colleges even provide bridge courses to enable non-science students to learn required concepts. Therefore, though a science background can be helpful, it is not a must for studying BCA.