At the time, the Dade County School Board was part-owner of the VHF channel 2 allocation in the market as part of a shared-time agreement with Community Television Foundation of South Florida, owners of WPBT. Under the original arrangement, the School Board operated the channel 2 frequency for five hours each day as WTHS-TV, carrying instructional television during the daytime hours, while the Community Television Foundation would take over the channel for two hours each evening to broadcast WPBT. Community Television Foundation had already begun increasing WPBT's operating hours, a process that accelerated with WSEC's sign-on. The 1970 formation of PBS brought a further increase in WPBT's broadcasting hours. By the late 1970s, PBS had grown enough that the split-time arrangement no longer made sense for a market of Miami/Fort Lauderdale's size. In 1979, the Dade County School Board returned the WTHS license to the FCC, while WPBT took over channel 2 full-time. Most of WTHS' educational programming moved to WSEC, which changed its call letters to the current WLRN-TV, to match its sister public radio station. Gradually, WLRN-TV evolved into a secondary PBS station for South Florida, alongside WPBT. WLRN began airing PBS’ journalism documentary series Frontline on October 14, 2018 after WPBT declined to air it.