The Thompson family in Minneapolis had three kids: ages 14, 16, and 18. Their forecast showed manageable college costs because they modeled each child separately.

The reality of overlap crushed them:

• Year 1: One in college, $28,000 out-of-pocket
• Year 2: Two in college, $52,000 (not $56,000 due to increased financial aid)
• Year 3: Three in college, $71,000 (better aid, but still devastating)
• Year 4: Two in college, $54,000
• Year 5: One in college, $29,000

They forecasted $28,000 maximum annual outlay. They hit $71,000.

The problem was modeling kids in sequence instead of parallel. With multiple children close in age, you face peak expense years that dwarf the average. Financial aid helps, but income and asset formulas change when multiple kids are enrolled.

Better forecasting means mapping the overlap explicitly. Identify your peak years. Model how financial aid calculations change with two or three enrolled simultaneously. Build savings to front-load the heavy years.

The Thompson family now has separate buckets: immediate expenses, peak year reserves, and final year completion funds. They're working extra hours now during the lighter years to prepare for the tsunami ahead.