CHICAGO (STMW) - Chicago Public Schools are pushing back the start of key state exams by one week, to the second week of March, after schools complained that snow days had swallowed up their test preparation time.

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The announcement Wednesday by Chicago Schools CEO Terry Mazany follows a decision by the State Board of Education to offer school districts the option of delaying testing for the Illinois Standards Achievement Tests, or ISATs, by one week.

The two-week testing window originally was to begin the week of Feb. 28, with many schools starting testing March 1. However, some city public schools complained they lost preparation time due to two snow days last week, and a third day saw sporadic attendance after classes resumed but without bus service.

“To give you and your students more instructional time — as well as more time to prepare for the ISAT exam — we have worked with [the Illinois State Board of Education] and other school districts to push back the ISAT testing window one week,’’ Mazany told CPS principals by email Wednesday.

That means testing would start Tuesday, March 8. There is no school on March 7, which is Casimir Pulaski Day.

Under the federal No Child Left Behind law, state tests have taken on increasing importance. In Chicago, ISATs taken by third- through eighth-graders help decide whether a school should be closed — and even whether certain students can get into elite CPS programs and schools.

Delaying the ISAT is optional, said State Board of Ed spokeswoman Mary Fergus. But even the delayed start date is “within the normal timeframe,’’ she said.

“Districts asked for it,’’ Fergus said. “Some had as many as eight or nine emergency days this year. I don’t know all the reasons.’’

The test window for 11th-grade exams, which begins April 27, remains unchanged.

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