NEW YORK — Most Broadway shows saw modest increases at the box office in Week 14 (Aug. 25-31), getting a Labor Day weekend boost before the upcoming back-to-school downturn.Heading into its final frame on the boards, “Rent” ($796,662) was up a hefty $160,000 as auds turned out to catch the show before it closed Sept. 7. “Monty Python’s Spamalot” ($642,920) benefited from holiday traffic by climbing a healthy $125,000, while “Gypsy” ($757,129) stepped up by almost $100,000. Other tourist-friendly tuners posting gains included “Mary Poppins” ($939,867), rising more than $60,000, and “Chicago” ($604,213), capping off a relatively robust summer by playing to 93% capacity. Tony-winning play “August: Osage County” ($551,883) bumped up about $45,000. The Rialto’s total cume, however, was off, falling $180,000 to $17.2 million for 24 shows on the boards (or about $18 million including estimated grosses for “Young Frankenstein”). Drop can largely be attributed to the recently shuttered “Cirque Dreams Jungle Fantasy” and “The Phantom of the Opera” ($483,917) playing only four perfs due to a scheduled upgrade of the Majestic Theater’s sound system. Also off was “Grease” ($570,245), which played only seven perfs due to an air-conditioner malfunction that scuttled the production’s Sunday night show. Otherwise, losses were mostly unremarkable. The only previewing tuner on the Rialto, “A Tale of Two Cities” ($412,356), played to 72% capacity auds in its second week of previews, on the way toward a Sept. 18 opening. The 22 musicals grossed $15,852,409 for 92.4% of the Broadway total, with an attendance of 214,456 at 88.6% capacity and average paid admission of $83.39. The three plays grossed $1,308,520 for 7.6% of the Broadway total, with an attendance of 18,953 at 83.3% capacity and average paid admission of $69.08. Average paid admission was $82.09 for all shows.