Other mistake: While Charlie is trying to figure out what's wrong with the squad, when Captain Stanley, Roy and John are sitting around the table, there's a can of scouring cleanser which has yellow tape covering the "a" and "x" so all we see is the "ja" on the can, in order to hide its brand name, which is Ajax.
Continuity mistake: While Charlie is finishing up on the squad's engine, Captain Stanley hands Johnny the address in the canyon that has overgrown weeds, and when Johnny packs up the toolbox, Charlie holds out the roll of electrical tape and the combination wrench, with its open-end up. However, in the next shot the only thing Charlie holds out is the wrench, but with its box-end up.
Answer: I was rewatching a few first season episodes of Charlie's Angels (1976), and in S1xE6 "The Killing Kind," I recognized the same actor. So, to finally fully answer your question, the two baseball players in School Days are played by Rod Perry and Sean Fallon Walsh.
Super Grover ★