Well, it's back to school time, and Mr. Parrish has given us a trickier-than-usual Monday to usher in the new season of study. Many subjects are covered today. From Economics we have ZEROSUM (3D: Like a game with equal winners and losers) and NETLOSS (40D: Business setback recorded on Schedule C), from Science we see STAPH (9D: ____ infection), ETHYL (48A: Car fuel additive) (see also 11D: What's filled in a fill-up GASTANK), and DISSECT (13D: Cut up, as a frog), and from English/Vocabulary we get ATROPHY (41D: Wither away) and JAPES (5A: Mocking remarks). There's a little geography quiz in the NE, with 12D: and 16A: "African country bordering [each other]" ALGERIA & MALI. and then there's the History extra-credit question that separates the honors kids from the lower tracks (do they still track? I thought I heard that that had gone out of fashion some time ago) 17A: Socialite who inspired 1950's "Call Me Madam" PERLEMESTA. Knowing that one will surely get you a star.
And if you enjoy the subject of History, you will surely delight in ADLAI (4D: Old politico Stevenson), NAPALM (40A: Vietnam War weapon), and SUSIEQ (25A: 1957 hit covered by Creedence Clearwater Revival in 1968), all of which are a bit MUSTY (28A: Stale-smelling). YUPPIE (55A: One of a 1980s demographic) skews slightly newer, but not much.
The anagram theme is well-done, and the central revealer looks elegant, just sitting there in the middle by itself. There was some less-than-stellar stuff, but nothing too terribly bad. It might sound like I have been complaining, but I welcome a greater challenge in the early-week puzzles.
Oddest clue 25A: First word in many newspaper names (THE).