Reporting the news on Tuesday, Blick said the teenagers found bones, a skull and clothes.
Speaking to the paper, one of the pupils, a 14-year-old, said: “We were looking for something when we discovered the skeleton. It was hidden by branches and leaves. At first we didn't believe it was real.”
The students told their teacher, who called the police.
Winterthur police confirmed the discovery to news agencies, saying they had found a credit card near to the remains.
While the body has not yet been formally identified, it is likely that of a retired man who went missing three years ago, police said.