D.S.R. YEARS:
When construction began on Detroit's Thomas M. Cooley High School on Hubbell Street in 1927 — just three years after the surrounding area had been annexed to Detroit from Greenfield Twp. — transit service to that area was limited mostly to short feeder bus routes (many of which not yet launched) that connected to the Grand River streetcar line a mile or two away. The only immediate bus route at the time was the DSR's Puritan-Fenkell bus line, which provided bus service along Fenkell Street just north of the new school. An attempt was made in 1929 to launch bus service through the developing neighborhood along Hubbell Street when a "Hubbell" bus route began operating from Wyoming and Puritan, via Puritan and Hubbell streets, to Fenkell and Hubbell. This service was implemented on April 8, 1929. However, the Hubbell bus service through that (initially) sparsely settled area was short-lived and the service was discontinued three months later, on July 17, 1929.

The first reference of bus service along Hubbell Street to service Cooley High School appears to be in 1941, when service along Hubbell (between Schoolcraft and Fenkell) was operated as a branch service off the Schaefer bus route (launched on Oct. 6, 1941), but only on school days during A.M and P.M. school hours. It appears that the service continued to operate off the Schaefer schedule for a number of years. The next available information shows that by 1950, service to Cooley High was now being operated as a separate bus route, and was listed on a September 1950 issued DSR Transportation Guide Map as the "COOLEY HIGH" coach line.

While the DSR did operate a number of school runs for the Detroit Board of Education beginning in August 1940 — which lasted well into the mid-1970s — many were special "school spots" operating along already established routes, while others were special daily chartered-service "school runs" that picked-up children at designated locations, much like Detroit Public Schools (DPS) contracted school-buses do today. The Cooley High route was unusual in that it operated as a regular route providing local bus service along Hubbell Street. It was also listed on DSR routes maps along with regular streetcar and bus lines. Normally, DSR school spots and school runs were not listed on timetables or maps distributed to the public.

A January 1951 published "DSR Transportation Guide of 1951" describes the COOLEY HIGH coach route as follows:
Northbound—Schoolcraft and Grand River via Schoolcraft, Hubbell, Chalfonte, Sussex to Fenkell.
Southbound—Via Fenkell, Hubbell, Grand River to Schoolcraft.
A.M. and P.M. service on School Days ONLY.

By 1956, the route had been extended 1¼-mile northward to Outer Drive, with service hours now listed as "7:35 A.M. to 3:50 P.M. on school days ONLY." Although service to Outer Drive was still being listed on a 1960-61 DSR Service Map, a 1963 Service Map shows the route had now been extended ¾-of-a-mile north to Seven Mile Road. However, by the mid-1960s, the Cooley High route seems to have been discontinued as a regular bus route and no longer appeared on DSR Service Maps. In addition, the Cooley High route was never assigned a route number when the DSR began assigning route numbers to its bus routes in 1966. (see: DSR Route Numbers)

Although it appears that the Cooley High line had now been discontinued as a stand-alone bus route, this did not bring about the elimination of bus service along Hubbell Avenue directly to Cooley Senior High School. According to those familiar with the service, it appears that the Cooley High service continued to operate for a number of decades thereafter, well into the D-DOT years.