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Coding Club Budget Builder

Run the Coding Club Budget Builder MicroSim fullscreen

About This MicroSim

A first-year budget has two halves that behave completely differently, and conflating them is the most common mistake in a club's first funding conversation.

The sample year comes to $2,660. That sounds like a \(2,660-a-year club and it is not. **\)1,830 of it buys hardware once — Chromebooks, kits, a storage cart. Only $830** comes back every September.

Get that backwards and you fail in one of two ways. Ask a funder for $830 to start and you cannot buy the kit. Tell them the club costs $2,660 a year and you have promised an ongoing number you do not need and probably cannot sustain.

Cost per student is what turns a budget into an argument. "\(2,660" is a number a principal has to interpret. "\)221 per student in year one, $69 a year after that" is a sentence they can act on — and the second figure is usually lower than anyone expects, which is exactly why it is worth quoting.

One classification worth arguing about in your own club: a device replacement fund. It looks one-time because you bought the devices once, and it is recurring, because they last three years and a club that does not save for that has a cliff coming.

How to Use

  • The sim opens on the sample year-1 budget. Read the two bars before anything else.
  • Add an item with a name, an amount, and a type; click the × on any row to remove it.
  • Move a big number between recurring and one-time — remove it and re-add it with the other type — and watch the cost per student stay put while the ongoing figure moves a lot.
  • Change Students to your real club size.
  • Clear all empties the list so you can build your own from scratch.

Lesson Plan

Bloom level: Apply (L3) -- calculate

Learning objective: Given a set of named recurring and one-time cost line items and a student count, the learner calculates the total annual budget, the recurring-versus-one-time split, and the cost per student.

Before the sim (10 min). Ask the group to guess what a club costs to run for a year. The guesses will be either wildly high or wildly low, and both usually come from not separating setup from running.

With the sim (15 min). Build the club's actual budget together. Arguing about whether a line is recurring is the productive part — snacks obviously are, a laptop obviously is not, and a replacement fund is a genuine debate.

After the sim (30 min). Write the two-sentence version for a funder: what year one costs, what every year after costs, and what that is per student. That is the paragraph that gets read.

Check for understanding. Ask: "A funder offers to cover your recurring costs for three years. What have you still not solved?" The one-time costs, and the replacement of the hardware in year three or four. Recurring funding does not buy equipment.

Embedding This MicroSim

Paste this into any page of the book, adjusting the relative path to docs/sims/ for the page's depth:

<iframe src="../../sims/coding-club-budget-builder/main.html" width="100%" height="562" scrolling="no"></iframe>

Specification

The full specification below is extracted from Chapter 30: Budgeting, Fundraising, and Grant Writing.

Type: microsim
**sim-id:** coding-club-budget-builder<br/>
**Library:** p5.js<br/>
**Status:** Specified
**Template:** https://github.com/dmccreary/economics-course/tree/main/docs/sims/budget-builder

Purpose: Let a club leader build a full first-year budget out of individual line items, then see the recurring/one-time split and the resulting cost per student before committing to a real number.

Bloom Taxonomy: Apply (L3)
Bloom Taxonomy Verb: calculate

Learning objective: Given a set of named recurring and one-time cost line items and a student count, the learner calculates the total annual budget, the recurring-versus-one-time split, and the cost per student.

Instructional Rationale: A parameter-exploration pattern fits this Apply-level objective because the learner needs to add, remove, and reclassify several line items and immediately see the arithmetic consequences, rather than watch one pre-computed scenario play out.

Canvas layout:
- Left (60%): a stacked bar showing the recurring total and one-time total side by side, plus a large "Cost Per Student" readout
- Right (40%): a scrollable list of line items with add/remove controls, and the number-of-students input

Interactive controls:
- Button row: "Add Recurring Item" and "Add One-Time Item," each opening a name field and a dollar-amount field
- Per-item: a small "x" remove button
- Input (number): Number of students, default 12
- Button: "Load Sample Year-1 Budget" -- prefills the exact worked example above (internet, insurance, snacks, printing as recurring; Chromebooks, Moving Rainbow kits, robot kits, storage cart as one-time)
- Button: "Reset"

Behavior:
- Recurring Total = sum of all items marked recurring
- One-Time Total = sum of all items marked one-time
- Total Budget = Recurring Total + One-Time Total
- Cost Per Student = Total Budget / Number of Students, rounded to the nearest cent
- The stacked bar and the Cost Per Student readout recalculate immediately whenever any item, amount, or the student count changes

Default parameters: loads with the sample Year-1 budget from the worked example (12 students, $830 recurring, $1,830 one-time, $2,660 total, $221.67 per student)

Implementation notes: p5.js canvas with createButton and createInput controls parented to the sketch's own control div; store line items in a JavaScript array of {name, amount, type} objects so items can be added and removed without redrawing the whole layout from scratch.

References