Updated 11/30/12 – 5:36 p.m.

CHICAGO (CBS) – The Chicago Teachers Union accused the Chicago Public Schools system of “educational apartheid” on Friday.

CTU officials unveiled a new study that it said shows the problem of “under-used” schools in the system is a crisis created largely by the district’s focus on creating more charter schools.

Currently, about 140 schools in CPS are at least half empty, and some of them likely will be targeted for closure by the district.

CBS 2′s Dorothy Tucker reports the union said the move by CPS to close low-enrollment schools and build more charter schools amounts to “educational apartheid.”

CPS officials wouldn’t say how many schools they plan to close after this school year, but administrators don’t deny most are in black and Hispanic neighborhoods. Those neighborhoods also have most of the city’s charter schools.

According to the CTU study, the school system has opened up charter schools near existing neighborhood schools, depleting the student populations in those schools. As a result, those neighborhood schools wind up being half-empty, and targeted for closure.

It’s a practice CTU labeled “educational apartheid.”

“These policies are going to increase educational segregation. Educational segregation does not produce better results, it produces worse results,” CTU Vice President Jesse Sharkey said.

The report commissioned by CTU also reinforces the argument the union has always pushed: that charter schools are not better than traditional public schools.

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For example, the research found students in traditional elementary schools score in the 43rd percentile on reading tests, compared to the 33rd percentile in similar charter schools.

Charter school leaders, like New Schools for Chicago CEO Phyllis Lockett, have other numbers. The data they offered shows students at 51 out of 63 charter schools outperform their neighborhood on the Illinois Standard Achievement Test.

As for the CTU allegation that CPS policy amounts to “educational apartheid,” Lockett said, “The apartheid, in my opinion, would be to continue the status quo; continue to not provide other alternatives or options to families than a failing school option.”

CPS Chief Executive Officer Barbara Byrd-Bennett responded to the union’s accusations by saying the district is closing schools because “CPS simply has too many underused buildings and too few students.”

School administrators said the teachers are also fighting school closings, not just to support their students, but to protect union jobs.