A modular mounting system for institutional or classroom furniture or fixtures includes mounting rails that are attached to a wall surface in a horizontal orientation and that are vertically spaced. The mounting rails have a flat wall-mounting portion, with upper and lower T-shaped sections projecting therefrom, forming upper and lower U-channels and a central C-channel. The wall-mounting portion has a lower chamfered edge. Sections of mounting rail are aligned by a spline inserted into the C-channel. The system is infinitely adaptable to a wide range of changing uses for the classroom, with each element of the modular classroom furniture easily mounted to or removed from the mounting rail with only a screwdriver. The selectable elements include a flat panel accessory that rides between the upper and lower mounting rails, an accessory tray, and vertical rail members and casegoods in various configurations that attach to one or both rails.