Multi-Kid Discount Option

Shipped: tiered percent-off by child rank (2nd kid, 3rd kid, etc.), with the director choosing which fees it applies to (semester fee, class fee, supply fee, monthly tuition) and a per-semester override. A sibling's rank locks in at enrollment and survives a drop, so no one gets silently promoted to full price mid-semester. Shown to families everywhere it matters — enroll page, Stripe Checkout, invoice, print view, and receipt email — with the original price struck through and "you saved $X."