The St. Louis City public school changed dramatically at the turn of the 20th century, when William B. Ittner became commissioner of City schools and their architectural consultant. From 1897-1914, Ittner designed fifty schools in St. Louis and in twenty-five other states. His innovation came to be called an "open floor plan:" instead of the rectangular box of older school buildings, Ittner schools are designed with long hallways extending from a central block. By ranging classrooms on either side of these hallways, he was able to maximize the amount of light and air available to each room, and improved the circulation pattern. The exterior of the building changed as well. A large central block was highly articulated and decorated; flanking wings were more restrained, but displayed large banks of high windows with transoms. The end pieces repeated the decoration of the center block. Ittner designed schools in almost every current architectural style, but usually favored Tudor Revival or Georgian, a subset of the Colonial Revival style.
The William Clark School, at 1020 Union Boulevard, was designed by William B. Ittner in 1906. The central block, topped by a high shaped parapet, is flanked by two wings, with end pieces set perpendicular to the main structure. In the Jacobethan style, the school is symmetrical; its center entry recessed beneath three delicate arches carrying a balcony of pierced stone work. The front facade has a brick diaper pattern, with heavy stone quoins. Windows are tall, multi-light sash, set deeply into the wall surface. Stairs are withdrawn into two exterior towers, capped by bell-cast metal roofs.
Sumner High School was constructed in 1911, and also designed by Ittner. Its plan is similar to the Clark School, having a monumental three-story central section, with Ionic portico and bell-cast cupola. Two-story wings extend between the center block and two-story end pieces. The exterior design of the school is Colonial Revival, and presents multi-light windows under brick arches with keystones, and a central entry with classical enframement and segmental crown. The original Sumner high school, the first high school for African-Americans west of the Mississippi, was located in older, surplus school buildings until parental pressure for a better facility caused this building to be constructed in 1911.