An Illinois high school has just apologized to Matt Nagy ... after its football team's fans aimed a "Fire Nagy" chant at the Bears coach during its game on Saturday.
The Chicago headman was watching his son play for Lake Forest in its game against Cary Grove ... when in the second quarter, a "Fire Nagy" chant broke out from Cary-Grove's section.
Video from the scene shows the synchronized shouts were loud -- and frequent -- and Nagy no doubt heard them all.