There are lots of wonderful areas in the Lafayette area. Here is a link to the school API index which you might find helpful.
Lafayette offers many different typs of neighborhoods. There are older homes, newer homes, streets with or without sidewalks, gated communities and many other factors. The best areas are based on your particular preferences and needs. The broadest answer is that most of Lafayette is in one of the best school districts in California, but not all of the Lafayette addresses. So, generally, you want to be able to determine the difference. As a realtor that works the area, I would highly advise you to choose a realtor that can show you around and determine which areas of Lafayette fill your needs the best.
You can go to my website to search for areas and see if it offers enough information or contact anyone of us to meet with you and assist you in finding your best fit.