Wikipedia
KRET-TV was an instructional television station in Richardson, Texas on channel 23, which was on the air from 1960 to 1970. The station was owned by the Richardson Independent School District. The station was the first broadcast TV station in the nation to be wholly owned by a school district. The call letters "RET" stood for "Richardson Educational Television".
KRET began broadcasting February 29, 1960 with a broadcast range of about 20 miles; it broadcast only on weekdays eventually matching school hours, and not during the summer. It was actually the first education television station in the Dallas-Fort Worth area, signing on about 6 months before KERA-TV.
The studio was first located at Richardson Junior High School from 1960-1963, then at Richardson High School from 1963-1970. The station was converted on August 31, 1970 into a closed-circuit network named "TAGER".
The tower stood on the campus of Richardson High School before being taken down in the mid-2000s, to make room for expansion of the school building.
Channel 23 was later re-allocated to nearby Garland. The frequency remained dark until 1985 when religious broadcaster KIAB-TV signed on the air. The station was later sold to Univision and became KUVN-TV, the network's O&O for North Texas.