Research · High schools - Illinois · October 2026
How Many High Schools Are in Illinois? 1,028 Public and 243 Private
As of October 2026: Illinois has 1,271 high schools: 1,028 public and 243 private. The largest is Adlai E Stevenson High School in Lincolnshire, with 4,758 students in grades 9 through 12.
The table lists the 15 largest public high schools in Illinois by the number of students in grades 9 through 12.
Analysis: Test Prep Gurus (High School Reach, highschoolreach.com), October 2026. Figures and the table may be quoted with attribution to Test Prep Gurus.
The findings, in plain English
Illinois has 1,271 high schools. 1,028 are public and 243 are private. The 710 public high schools that report enrollment hold 584,254 students in grades 9 through 12 between them. The private count is a floor, because the federal private school survey is voluntary and a school can skip it.
Adlai E Stevenson High School is the largest public high school in Illinois. It enrolls 4,758 students in grades 9 through 12 in Lincolnshire. The 15th largest school on the table, Bolingbrook High School in Bolingbrook, enrolls 3,298. None of the 15 largest are charter schools.
The largest private high school in Illinois is Marist High School. It enrolls 1,657 students in Chicago. That is smaller than every public school on the table above. Private schools report total enrollment to the federal survey, so a school that also teaches younger grades counts those students too. Only schools whose lowest grade is 9 are listed here, so each one is a high school.
The 15 largest public high schools in Illinois
Ranked by the number of students in grades 9 through 12.
| High school | City | Students in grades 9-12 | Charter |
|---|---|---|---|
| Adlai E Stevenson High School | Lincolnshire | 4,758 | No |
| Lane Technical High School | Chicago | 4,389 | No |
| Taft High School | Chicago | 4,314 | No |
| Waukegan High School | Waukegan | 4,186 | No |
| East High School | Aurora | 4,020 | No |
| Lyons Twp High School | La Grange | 3,706 | No |
| Lockport Township High School East | Lockport | 3,678 | No |
| West Aurora High School | Aurora | 3,639 | No |
| Evanston Twp High School | Evanston | 3,560 | No |
| Warren Township High School | Gurnee | 3,537 | No |
| Joliet West High School | Joliet | 3,451 | No |
| J Sterling Morton East High School | Cicero | 3,394 | No |
| J Sterling Morton West High School | Berwyn | 3,374 | No |
| Oak Park & River Forest High School | Oak Park | 3,307 | No |
| Bolingbrook High School | Bolingbrook | 3,298 | No |
NCES Common Core of Data, grade 9-12 enrollment. Virtual schools are excluded. Absence from this list means a school is not among the largest, nothing more.
The largest private high schools in Illinois
Private schools whose lowest grade is 9, by total enrollment.
| High school | City | Students |
|---|---|---|
| Marist High School | Chicago | 1,657 |
| St Ignatius College Prep | Chicago | 1,473 |
| Benet Academy | Lisle | 1,265 |
| Fenwick High School | Oak Park | 1,101 |
| Depaul College Prep | Chicago | 942 |
NCES Private School Universe Survey 2021-22, respondents only. Total enrollment, not a grades 9-12 count.
What these counts cover
A high school here is a school that serves grade 12. Virtual schools are left out, because a school with no building is not comparable to one with a campus. Public counts come from the federal Common Core of Data, which every public district reports to. Private counts come from the federal Private School Universe Survey.
Enrollment for public schools is the number of students in grades 9 through 12, so a school that also teaches middle school grades is not inflated by them. A school that reports no enrollment figure is counted in the state total but cannot be ranked, which is why the number of schools with an enrollment figure is smaller than the public count.
Private high schools in Illinois
The private table below shows the largest private high schools whose lowest grade is 9. The survey is voluntary, so treat these as the largest among the schools that answered, not a complete ranking. A private school that declines the survey does not appear at all.
Private enrollment is a total, not a grades 9 through 12 count, because the survey does not break it out the same way. Limiting the list to schools that start at grade 9 keeps the figures comparable to each other.
What a family should do with this
Size is a starting point, not a verdict. A large school usually offers more courses, more sports and more clubs, and a small school usually gives a student more contact with the adults who write recommendation letters. Both shapes send students to good colleges.
The more useful question is where a school's own graduates actually go. Our page for each Illinois high school carries that school's figures and, where the school publishes one, its own numbered list of the colleges its graduates chose. Start from the school page rather than from the size of the building.
Questions parents ask
How many high schools are in Illinois?
Illinois has 1,271 high schools: 1,028 public and 243 private. The largest is Adlai E Stevenson High School in Lincolnshire, with 4,758 students in grades 9 through 12.
What is the largest high school in Illinois?
It enrolls 4,758 students in grades 9 through 12 in Lincolnshire.
Are private high schools included in the Illinois count?
1,028 are public and 243 are private. The private count is a floor, because the federal private school survey is voluntary and a school can skip it.
Method & sources: Public school counts and grade 9-12 enrollment come from the NCES Common Core of Data; private counts and enrollment come from the NCES Private School Universe Survey, whose respondents are a floor. A high school is a school serving grade 12; virtual schools are excluded. The public table is ranked by grade 9-12 enrollment, and schools without an enrollment figure are counted in the state total but not ranked.
This brief as data: /research/high-schools-in-illinois.json. Free for editorial use with attribution to Test Prep Gurus (High School Reach).
Related: How many high schools are there in each state? · The 50 largest public high schools in America · Do Illinois public universities require the SAT or ACT?