On getting less money from the state (and running your numbers)

I'm always hesitant to do this, because I want to encourage local reporters to cover education issues including funding, and I'm always a bit concerned that this will come off as hammering them, when in many cases they're really trying. In a lot of cases, though, it's less the reporter than the local official(s) who are either not understanding or are willfully misrepresenting what's happening, and clarity, when it comes to education funding, is really important.
In this case from Foxborough, I think there's just more that needs to be explained. When we're talking about a print paper, I'm well aware that space is an issue; it's why this blog exists, for example. The online universe, though, allows for more room, and I would really encourage local papers to take advantage of that.
In Foxborough's case, let's first specify that their Chapter 70 aid is about 19% of their foundation budget. Their foundation budget for FY19 is $28.6M; their combined effort yield--what I'd call "what can the town afford to pay"--is $23.5M. I can't find the FY19 budget online (I hate that), but the district spent $38M in FY17, so I'll venture they're spending well over $28M for this coming year, as well.
Foxborough for FY19 is a minimum increase district; they're not seeing an increase due to changes in their enrollment and such, so they're getting $30/pupil as an increase, which is $79,680.
That isn't the only place the district gets state aid from, however, and this is where the catch comes in; the town is speaking of net aid, and they're adding in the charter reimbursement, as well.
And here's where I raise an eyebrow:

The town has received $77,940 less for fiscal year 2019 compared to last fiscal year, and assessments have increased by $29,059, according to data on the state Department of Revenue website.
“The net state aid went down by over a $100,000,” Town Manager William Keegan said. “It was unfortunate, and we didn’t anticipate this.”

The Department of Revenue report discussed is here; if you type in Foxborough, you'll see Foxborough receives $9.3M in aid this year; there's $375,815 in charter reimbursement added to the Chapter 70 aid.
Last year, though, Foxborough received $531,275 in charter reimbursement, added to their $8.8M in Chapter 70 aid. So there's a net loss.
But...they didn't anticipate this? Remember, charter reimbursement comes for CHANGES in charter enrollment (charter kids getting more kids or more expensive kids), and it's supposed to be 100% the first year, and 25% for three years after that. Now, the out years have never been funded, so please tell me Foxborough wasn't counting on that, but even so, unless their local charter schools were getting significantly more pupils, Foxborough was always going to receive less in charter reimbursement than they had the prior year.
The one thing that is a wrench in the deal is the state is only funding the first year reimbursement at what looks like 90.9%, so if Foxborough (and others) were counting on 100%, there is a difference. It's a difference of only $37,605, though.
Once Foxborough had its spreadsheet on aid and knew it would only get a minimum increase, and once it had the projections DESE shares on charter enrollment...they could have figured this out.
And this line:

He added that efforts at the state level to get reimbursed for 100 percent of charter school costs, including a bill filed by state Rep. Jay Barrows, had been unsuccessful.

...muddies the issue, as currently, districts aren't, by law, even promised reimbursement of 100% of costs, just 100% of reimbursement of changes in the enrollment. 

Remember: you're a better advocate if you can accurately represent your complaint!