In one week the fall season officially begins with the first of—count ’em—two dozen new shows. To make things easier this year, I’ve decided to grade the new shows. As every student knows, grades are arbitrary and unfair—but that’s just what makes them such fun for teachers and critics. The scale is simple: A+ is reserved for the very best (there’s only one this season); A means it’s good; B means it’s above average; C means average at best; D stands for dud; and F is reserved for shows that make you want to throw your TV out the window and then go downstairs and burn it. A few shows sneaked in early before the fall semester began, but I’m grading them too. To wit: Hometown, CBS’ slushy Big Chill, earns a C. West 57th, CBS’ lite-news show, also earns a C—barely. American Almanac, NBC’s new news show, gets a B. And this week, at 8 p.m. on Sept. 4, NBC reruns its pilot for Hell Town with Robert (Baretta) Blake starring as a tough ghetto priest. Based on the pilot, I’m giving that a B, but it could be raised to an A later in the term. Class dismissed. For extra credit this week, we offer a couple of cable shows and a syndicated series about the long arm of the law reaching across the Atlantic.