Assigning financial responsibility to towns in a regional school district is never a simple or easy task. Numerous factors must be weighed and choices made among the many possible ways to divvy up costs.

When developing the Monomoy Regional School District agreement, Chatham and Harwich officials opted to use a three-year rolling average of enrollment to determine how much of the district budget each town would cover. When the district was established a dozen years ago, Harwich's percentage of the total enrollment was about 72 percent, with Chatham at 28 percent; this year, that split is 76.56 for Harwich and 23.44 for Chatham. Next year's proposed school budget of $44.3 million represents a 3.8 percent increase for Harwich and a 1.5 percent increase for Chatham.

Harwich's rising percentage of the budget, a more than $1 million increase next year, concerns town officials, who last week suggested that it's time to re-examine the funding formula in the regional agreement. There's no harm in this, and another formula may, in fact, mean lower costs for Harwich. But it's important to remember a few things. First, regionalization was driven by Harwich's need for a new high school. By merging with Chatham, the town saved millions over the cost of constructing its own stand-alone high school. For the first time this year, each town will pay the operating costs of its own elementary school, essentially saving Harwich more than $700,000. That move was driven by Harwich, and Chatham gladly acquiesced, even though it increased the town's costs by the same amount that Harwich saved.

But enrollment figures don't lie. Even though the number of students from both towns has been steadily declining since regionalization, Chatham's drop has been more precipitous. Harwich simply has more kids. That's not something officials should be grousing about; it's a sign of a healthy, diverse community.

School costs are rising everywhere; witness the Nauset Regional District's 7.6 percent proposed increase, which has officials in that district's towns on edge. We don't oppose to considering different funding formulas for the Monomoy district, but caution that it may not create the sort of savings Harwich officials are looking for. Any change will also require ratification by both towns, and a shift not based on a fair examination of the numbers will be a hard sell.