Daniel Desario is shown sitting down and listening to the Black Flag song "Rise Above," and although it was originally recorded earlier to appear on a single, the song was not actually released until December of 1981 on the album "Damaged." Since the single season of the show takes place over the course of the 1980-1981 school year, this album would not have been released until halfway through the next year of school.
During the opening title sequence to the episode "Noshing and Moshing" while Daniel, Ken and Nick are in the liquor store, the cooler behind them contains flavors of Gatorade Frost that were not introduced until 1998. The show is set in 1980.
When Daniel, Nick, and Ken are at the punk rock show, a Mesa Dual Rectifier amp head is visible on stage being used by the band (immediately following when Barry is asked, yet again, if he's chosen a major). However, this amp was not released until 1989.