Projection of Impact of Charter Opening on Traditional District Finances

(Kindergarten through 8th Grade)
Projection details and FAQs
About the model
This page simulates the effect of charter school's expansion or opening on the finances of public school districts. The model shows enrollment changes and financial impact for K-8 only. The model uses 2014-2015 state data for each district, including total enrollment, number of schools, teacher salaries, per pupil spending, and maximum class size. Data are available here: It is based on what has happened to districts in the past when charters open or expand.
About us
We (Stephanie Hirsch and Joe Calzaretta) are parents of three children in the Somerville Public Schools. Stephanie Hirsch has spent almost 20 years working in the analysis of finance and operations data at the state and local level. She studied finance at Harvard Business School and the statistics at the University of Chicago and she believes in strong local government and strong community institutions. Joe is an MIT-trained software engineer and mathematician. Contact us at

What happens to funding when a child leaves the district for a charter school?
When students leave a traditional district for a charter, the district loses the local tax dollars that pay for that student's education, not just the state aid. In comparison, when a student goes to a private school, the state aid is lost but the tax dollars – usually most of the per pupil expenses -- stay with the community.
What assumptions does the model make?

How Students Leave: Based on prior real-life cases, we assume that a new charter school will draw a certain number of students from the public school district every year. (You can change this number in the projection.) Often new schools open with one grade at a time, starting at K or at the start of middle school or high school. For the first year, there will be a larger draw from Kindergarten than from the other grades. In the second year, there will be a larger draw from 1st grade. This process continues for each year, targeting each successive grade level, until the ninth year where there will be a larger draw from 8th grade. Specifically, the projection tries to draw 60% of students from the targeted grade, and then draws the remainder from all grades equally. These students are chosen randomly (to try to replicate what actually happens), which means that each run of the projection may result in slightly different outcomes.

What the District Does: We assume that the district will try to close sections to save money, as section teachers cost a certain amount per year. (We have added $18K to the teacher salary from the state data to account for benefits. You can also change the teacher salary number in the projection. ) The district has a maximum allowable number of students per class section (You can change this number in the projection.) The district will keep the fewest number of sections without exceeding this maximum class size. That is, each school will freely move students between sections in a grade in order to close class sections, but students are not moved across grades or across schools, even if this would result in fewer class sections. We based the maximum class size on the largest class size we found in the district’s data for grades K-8 (however you can adjust that number in the model).

Other Details: We assume:

  • Each section has one teacher.
  • If the district is chosen from the dropdown, the K-8 enrollment for each grade in each school in the district is initially chosen to match the 2014-2015 information published by the state. (Note that this will differ slightly from actual enrollment, but it will be close). If the district is not chosen from the dropdown, you can choose the number of schools and the initial number of students in the district, and the total district K8 enrollment is distributed evenly across grades and schools at the start of the projection.
  • The per pupil expenditure shown in the model has been reduced from the state data by 10% to account for the average effects of state facility aid (about 7%) and the deviation between the amount that districts pay for charter tuitions (about 3%). For districts that are currently making tuition payments, they can find their payment and state facility aid in this report and can plug it into the per-pupil spending to get a more precise cost projection.
  • Each district is assumed to have a number of support, intervention, and enrichment teachers at the start of the projection. These teachers are assumed to have the same yearly salary as the class section teachers.
  • According to state law, districts receive some funding during a transitional period when a student leaves. This program aims to maintain full funding for a student the first year after she leaves the district, and then 25% funding for each of the next five years, before dropping to zero funding entirely starting in the seventh year. (Explained here: However, this program has not been fully funded in recent years, and a significant gap remains in the FY17 Governor’s budget. Thus, the district only receives a fraction of each departed student's reimbursement each year (e.g. 59% of 100% in year one, and 59% of 25% in years 2-6). (The default level is 59%, however you can change this number in the projection to model different State funding scenarios).
Why is there such a big deficit?
As the projection progresses, the net loss of funding for departing students quickly becomes greater than the savings in teacher salaries by closing sections. This is because too few students leave from any one grade/school to close sections. Also, the district has fixed costs that don't disappear when a student leaves, like the salary of a payroll coordinator or superintendent. To close the budget gaps, the district will need to cut the extras — like reading teachers, school counselors, specialists (music/art), pre-kindergarten programming, and any other student service or support. If the projection shows that these are completely eliminated, and the budget drops below zero, it means that the district will need to cut costs in ways not accounted for by the projection.

What else can districts do to cover the deficits?
Instead of cutting enrichment and support, districts can close schools to cover the annual deficit. However, because no one school will lose all of its students, this means moving students who remain in the shuttered school to a new school. That’s a very disruptive and politically difficult, so sometimes doesn’t happen as planned. Alternately, a city can cut other city services (e.g. recreation, health and human services, police/fire) to cover increased funding for the schools.

How long will the deficits last?
With no cap, the deficits may continue until every school has been turned into a privately-run public charter school.

Where can I learn more?
We welcome a lively discussion on the model, as more information will help districs and voters make a decision on Question 2. Join the discussion at:

How can I see your code and math?
close details

Students lost:
Teacher reduction:
Sections closed:
Total funding lost:
Cuts made:
Additional cuts needed:
Enrollment details
Funding details
Year Total funding lost Sections closed Additional cuts needed