How the enrollment forecast works

Iowa City Community School District · Grades K–12 · 30 June 2026

The big idea in one paragraph

Every October 1, Iowa schools count every student by grade. We use those counts to measure how many students in each grade "stay" in the district as they advance to the next grade the following year. Call that fraction the grade-progression rate: if 1,000 third-graders are enrolled this fall and 978 fourth-graders show up next fall, the rate for that transition is 0.978 — about 2% of the cohort didn't return. Apply those rates to the current enrollment and you get a year-by-year enrollment forecast. Kindergarten is handled separately: because there's no prior grade to track, we project it from the number of babies born in Johnson County five years ago, adjusted for the fraction of those children who actually end up enrolling in this district.

Step 1: Measure how many students stay year to year

For each grade and each year we have data, we compute:

rate = students in grade G+1 this fall ÷ students in grade G last fall

Worked example — 1st grade to 2nd grade, 2024 to 2025:

1 1st-graders counted in October 2024: 965

2 2nd-graders counted in October 2025 (Iowa DOE verified data): 1,013

3 Rate: 1,013 ÷ 965 = 1.050

4 The cohort grew 5.0% going from 1st to 2nd grade — more students transferred in than transferred out.

A rate above 1.0 means the cohort gained students (families moving in, students transferring from other districts). A rate below 1.0 means it shrank (moves, transfers out, private school). The 8th-to-9th-grade transition typically shows a gain as students consolidate into Iowa City's comprehensive high schools. The 9th-to-10th and 10th-to-11th transitions tend to show small losses.

The full table of rates, every year and grade. Yellow shading = school years disrupted by COVID (these years are given only 30% weight in the average). All columns use verified Iowa DOE fall enrollment counts for both years.

Grade	2016→'17	2017→'18	2018→'19	2019→'20 🟡	2020→'21 🟡	2021→'22	2022→'23	2023→'24	2024→'25
K→1	0.988	0.994	1.015	0.923	1.058	1.001	0.993	1.040	0.996
1→2	0.998	0.972	0.993	0.924	1.057	1.005	0.993	0.995	0.976
2→3	0.990	0.993	1.024	0.960	1.004	0.996	0.991	1.015	1.006
3→4	1.006	0.986	0.998	0.956	1.021	1.002	0.983	1.016	1.005
4→5	0.985	0.996	1.011	0.978	0.994	0.986	0.995	1.010	0.995
5→6	1.009	0.998	0.996	0.970	0.993	1.007	0.999	1.009	0.995
6→7	1.011	1.003	1.042	0.984	1.021	1.013	1.044	1.015	0.992
7→8	1.004	0.991	0.994	0.989	1.001	1.025	1.006	1.030	0.991
8→9	1.078	1.025	1.044	1.038	1.040	1.053	1.027	1.073	1.037
9→10	1.026	1.032	1.036	1.009	1.027	1.007	1.006	1.053	0.996
10→11	1.019	1.003	0.999	1.004	1.003	1.007	1.017	1.000	0.997
11→12	1.084	1.027	1.057	1.031	1.054	1.053	1.028	1.038	1.043

🟡 COVID year (weighted 0.3× in smoothing). All columns use verified Iowa DOE BEDS data for both origin and destination years.

Step 2: Average the rates, with more weight on recent years

We don't treat every year equally. COVID (the 2019-20 and 2020-21 school years) distorted enrollment in ways that don't reflect normal district behavior — fewer kindergarteners showed up, and families made unusual grade-transition decisions. So those two transitions count for only 30% of a normal year in the weighted average. The two most-recent school years count double (2×), because recent patterns are more predictive than older ones.

Each of the three scenarios uses a different set of years:

High scenario: uses all available years (same grade-retention rates as the Baseline), but assumes in-migration from Iowa City's growth corridors strengthens enough to push the effective K-entry share up to 0.740. Grade-to-grade retention is the same as the Baseline; the difference is in kindergarten headcount only.
Baseline scenario: uses all available years with the COVID discounts described above. Kindergarten share stays at 0.728 — the current calibrated level.
Low scenario: uses only the most recent two school years (2023–2025), giving more weight to the recently observed pattern. Combined with a lower K-entry share (0.680), this tests the case where in-migration slows and the share decline continues.

Smoothed rates used in each scenario:

Grade transition	2016–2022 avg	2023–2025 avg	Low scenario	Baseline	High scenario
K→1	0.997	1.018 +0.021	1.018	1.006	1.006
1→2	0.994	0.986 -0.008	0.986	0.989	0.989
2→3	0.996	1.010 +0.014	1.010	1.003	1.003
3→4	0.994	1.010 +0.016	1.010	1.001	1.001
4→5	0.993	1.003 +0.010	1.003	0.997	0.997
5→6	1.000	1.002 +0.002	1.002	1.001	1.001
6→7	1.023	1.003 -0.020	1.003	1.013	1.013
7→8	1.006	1.010 +0.004	1.010	1.006	1.006
8→9	1.043	1.055 +0.012	1.055	1.049	1.049
9→10	1.017	1.025 +0.007	1.025	1.023	1.023
10→11	1.009	0.998 -0.011	0.998	1.004	1.004
11→12	1.047	1.040 -0.007	1.040	1.045	1.045

A positive shift (2023–2025 vs. 2016–2022) means grade retention has improved in recent years. Negative means more attrition. Cause of any shift is not established.

Step 3: Project kindergarten from birth data

There's no prior grade to roll forward into kindergarten, so we project it differently: from birth records. The number of babies born in Johnson County five years ago is a strong predictor of how many kindergarteners will walk through Iowa City's doors. We pull Johnson County resident birth counts from the CDC's national birth records database and apply a multiplier to account for the fact that the Iowa City district boundary doesn't match the county line, and that not all county residents enroll in this district.

Projected kindergarteners(year) = Johnson County births(year − 5) × district share

How we calibrated the share. In October 2025, the Iowa DOE verified count showed 987 kindergarteners enrolled in Iowa City schools. Five years earlier, in 2020, there were 1,356 babies born to Johnson County residents. So:

1 Johnson County births in 2020: 1,356

2 Five-year lag → these children entered kindergarten in fall 2025

3 Actual kindergarteners in fall 2025 (verified): 987

4 Share: 987 ÷ 1,356 = 0.728

5 District share = 0.728 — 72.8% of Johnson County births enrolled in Iowa City schools five years later.

The observed shift since 2023. The kindergarten count has declined three straight years (1,035 in fall 2022 → 998 → 992 → 987 in fall 2025). The effective district share of county births has fallen from a 2016–2022 average of about 0.742 to a 2023–2025 average of 0.718. The 2025 figure (0.728) sits between these averages. Multiple factors can affect this share simultaneously — migration, private-school enrollment, open enrollment across district lines, and the geographic mismatch between county and district boundaries. We do not have enrollment-transfer data to isolate any single factor as the cause. The three scenarios test different assumptions about where the share goes next, without asserting why it moved.

Forecast kindergarten counts, by scenario:

Birth year	Johnson Co. births	Kindergarten year	High (share 0.740)	Baseline (share 0.728)	Low (share 0.680)
2021	1,312	2026	971	955	892
2022	1,298	2027	961	945	883
2023	1,280	2028	947	932	870
2024	1,265	2029	936	921	860

Births are declining across Johnson County — a national demographic trend. The same births data is used in all three scenarios; only the share changes.

Step 4: Roll the forecast forward

Starting from the October 2025 verified enrollment (14,227 total), we apply the smoothed rates to project each grade one year at a time. Kindergarten comes from the birth formula above. Each subsequent grade comes from the grade below it, multiplied by its rate. We do this for five years (2026 through 2030), accumulating any compounding errors as we go further out.

The five-year window is intentional. Beyond five years, birth trends and migration patterns become too uncertain to be useful, and the honest answer is a wide range rather than a point estimate.

The three scenarios — what they mean in plain English

High — "Growth holds"

What has to be true: The North Liberty and Tiffin growth corridors keep building homes and attracting young families at today's pace or faster. More children move into new houses than the birth trend would predict, pushing the district's effective share of county kindergarteners slightly above today's level — to 0.740. Grade-to-grade retention for students already in the system follows the same overall pattern as the Baseline. The scenario differs from the Baseline only in how many new kindergarteners enter each year.

2030 enrollment: 13,551. Still below the 2025 level due to falling birth counts, but the decline is modest. This scenario requires sustained housing construction in the growth corridors.

Baseline — "Current trajectory holds"

What has to be true: Roughly what's happening now continues. In-migration from the growth corridors continues at roughly today's pace. The district's share of county kindergarteners stays at 0.728 — the same rate calibrated from the 2025 actual data. Birth counts keep falling gradually. No major disruption in either direction.

2030 enrollment: 13,475 (-752 from 2025, -5.3%). A slow, steady decline — roughly one class per grade per year smaller than today. The decline is driven by fewer births, not school closures or a financial crisis.

Low — "In-migration slows, share declines"

What has to be true: New construction in North Liberty and Tiffin slows as the most buildable land fills in — fewer families moving into the district each year. The district's share of county kindergarteners falls to 0.680 — about 35 fewer kindergarteners per year than births would predict. Grade-to-grade retention follows the post-2023 pattern, which shows slightly more attrition than earlier years. The cause of the share decline is not assumed; this scenario tests the lower bound of the observed range.

2030 enrollment: 13,306 (-921 from 2025, -6.5%). Roughly the equivalent of closing one elementary school's worth of enrollment from the current level.

What could make this wrong

The grade-progression rates rest on 10 school years of verified Iowa DOE enrollment data (2016–2025). The main remaining structural uncertainty is open-enrollment flow: Iowa lets students attend school outside their home district, and if Iowa City's net in/out balance changes — for example, because a neighboring district opens a new school or becomes more attractive — the grade-progression rates won't capture it cleanly. Adding annual open-enrollment in/out data (published by the Iowa DOE) would separate in-district retention from cross-district transfers.
The district share (0.728) is one number capturing many things. It combines the geographic mismatch between county and district boundaries, private school choice, Iowa's open-enrollment policy (students can cross district lines), and any structural shifts in who enrolls. A richer model would track each of these separately. For now, the three scenarios capture the range of how that single number might shift.
Johnson County births for 2023 and 2024 are still estimates. The CDC's national birth records typically lag two years before becoming final. These figures will be updated when final counts are published.
Iowa's open-enrollment policy adds noise. Students can attend public school outside their home district. If Iowa City's net flow of students crossing into or out of other districts changes — for example, due to rivalry with neighboring districts or a new school opening — the grade-progression rates won't capture it cleanly.

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