First Church of Christ, Scientist, Long Beach and Palo Alto, CA
As a new denomination in the range of Protestantism at the end of the 19th century, Christian Science had no precedent for the appearance of its churches. The Mother church in Boston provided one pattern, but architects were often left own inclinations. S. S. Beman in Chicago designed dozens (perhaps an exaggeration) and, of course, Bernard Maybeck built only two. Another architect who may have been a convert to Christian Science was Elmer Grey, who produced churches for both Long Beach and Palo Alto in California. The first of these, as you will note from the published plan and interior, is an F-1 — the Sunday school is in the lower level.
At Palo Alto the Sunday school is essentially a single room hung on the site of a diagonal auditorium, hence D-3: