Your school district decides most of your bill
Schools commonly take the majority of an Illinois property tax bill, which is why identical houses differ.
Owners comparing bills across towns often conclude one assessor is harsher. Usually the difference is the school district.
The share
School districts commonly account for the majority of an Illinois property tax bill — frequently well over half. Municipal, county, park, library and township levies divide the rest.
Why neighbours differ
District boundaries do not follow municipal ones. Two houses on the same street can sit in different elementary or high school districts with materially different rates, and nothing about either assessment is wrong.
What it means for an appeal
A high rate makes a reduction worth more, but it is not itself a ground. You cannot appeal your way out of a district. If your assessment is fair and the bill is high, the assessment system has done its job and the question is a budget one.
What it means when buying
Compare the rate, not just the price. A cheaper house in a higher-rate district can cost more to hold, and the difference compounds every year you own it.