Released during 1979 production, International Harvester introduced the S-series bus chassis alongside its conventional-cab counterpart.

[1][2] In a shift from being an adaptation of a truck chassis, the Schoolmaster was designed as a distinct model line intended solely for bus use.

For 1987, the grille underwent a revision, with the "International" wording moved from the top of the grille to the bottom left, paired with Navistar's famous "Diamond Road" logo (replacing the IH logo on the steering wheel).

Along with powertrain configurations, the two model ranges were distinguished largely by suspension weight capacities.

Over its 15 years of production, the second generation of the S-series chassis underwent few changes, centered around revisions to its powertrain.

A key event that would affect school bus manufacturing during the later 1990s was the completion of the acquisition of AmTran by Navistar in April 1995.

By the end of the decade, AmTran buses would begin to start wearing International badging on the body as well.

As it was a change intended to promote IC Corporation, chassis destined for Blue Bird or Canadian manufacturer Corbeil were still received with the standard hood and grille design.

Using the low-profile International 4700LP as a basis, the 3400 has been among the largest vehicles developed as cutaway cab chassis.

After 2001, International ended production of the 4000-series; the 3400 was replaced by the 3200 based upon the new-generation 4000-series trucks (later the DuraStar, today the MV).

In comparison to the 3800, the driver of the Vista sat further forward (shifted nearly atop the front axle instead of behind it).

In line with a transit-style bus, the driver sat next to much of the engine; access from the front was also maintained via a tilting hood (shortened in length by nearly half).

As the 3600 chassis was developed alongside the 1991 update for the Thomas Vista body, it was never used on another product line.

While produced as a bare chassis, the model line shared the steering column and instrument cluster from the S-series conventionals.

During the late 1990s, the market share of International grew as several body manufacturers (Wayne and Carpenter) closed down; while Freightliner began chassis production in 1997, Ford and General Motors were gradually phased out of full-size chassis production.

At the time the 3800 ended production in 2004, the number of full-size body manufacturers from 1979 had decreased from eight to three (Blue Bird, Thomas, and IC, the successor to AmTran/Ward); International was the sole remaining chassis manufacturer (following the exit of Ford and GM, Freightliner and Blue Bird commenced production of cowled chassis).