Story highlights Musician Tim McGraw posted a video of the students singing

One teacher wrote that it was a spur-of-the-moment decision

(CNN) A lesson in compassion isn't something you expect from high school students.

But a group of 400 students from Nashville's Christ Presbyterian Academy showed up outside the home of a cancer-stricken to sing songs of worship when he could no longer teach.

Ben Ellis, who teaches Latin and Bible studies at the school, is battling an aggressive form of cancer.

He had been teaching until last week, working through his chemotherapy and radiation treatments because being at work helped him through it.

Last Wednesday, he was having a tough morning after getting some hard news the night before, said Nate Morrow, the school's headmaster.

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