Standard & Poor's Ratings Services said it raised its rating on Cook County School District No. 171 (Sunnybrook), Ill.'s general obligation bonds to AA-minus from A-plus.
The outlook is stable.
"The upgrade is due to a substantial improvement in cash reserves," said Standard & Poor's credit analyst John Kenward.
The rating reflects the district's: participation in the deep and diverse Chicago metropolitan area economy; very strong income level; and very strong cash reserves.
The district serves an estimated population of 11,015 in Lansing and is located 25 miles south of downtown Chicago.