Want to frustrate anyone involved in reclassifying Maine’s high school sports teams every two years? Mention “enrollment differential.” Changing demographics and a shrinking high school population have challenged organizers within the Maine Principals’ Association. The MPA uses enrollment to determine sports classification in an effort to maintain competitive balance for a membership that ranges from 18 students at North Haven School to 1,476 at Thornton Academy in Saco. MPA football organizers recently reached a temporary fix caused by the enrollment differentials within Class A by reducing that field of large-school programs from 14 schools to eight for the next two years. That proposal awaits final approval Thursday from the MPA’s general membership. Basketball has experienced similar struggles in its smallest classes to minimize the enrollment differences between their largest and smallest schools — to the point that two different proposals await consideration by the MPA membership. That’s a first for Dick Durost, who is retiring this summer after serving as MPA executive director since 2001. “What we try to do,” he said, “is give schools every opportunity to compete for a spot in the postseason, but I don’t think we can guarantee anyone an opportunity for a gold ball once they get there.” While football has sought to address this issue in Class A where the enrollment differential between its largest and smallest schools has reached 500 students or more, the basketball proposals are different by only 10 students in separating the two smallest-school divisions, Classes C and D. But the basketball issue is larger than the fine line between the dueling recommendations. The seven largest schools in Class C North last winter — led by Central of Corinth and Houlton with 324 students apiece — each had more than double the enrollment of the three smallest entries, Central Aroostook of Mars Hill (137), Hodgdon (137) and Fort Fairfield (134). In Class D North, Schenck of East Millinocket and Washburn led with 118 students each followed by Machias (115), and Deer Isle-Stonington and Woodland (112 each).