A 16-year-old boy was stabbed by another teen at a high school near Milan on Tuesday, the second school stabbing in as many days in the northern Lombard region after a teacher was knifed by a student.

Authorities were questioning the suspected aggressor, a 17-year-old boy, the news agency LaPresse reported. The motive for the stabbing at a vocational high school south of the city was unclear. The victim was rushed to a hospital for treatment of a stab wound to the thigh.

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Police on Monday arrested a 17-year-old student in the city of Varese, north of Milan, for investigation of attempted murder after stabbing a 57-year-old teacher multiple times in the back as she entered another vocational school. The school said that the student had behavioral issues and was being given special attention "to improve his psychological and attitudinal abilities."

The GILDA-UNAMS teachers' union has underlined rising acts of aggression in schools after Monday’s stabbing.

"It is necessary that we face the problem of guaranteeing safety in the schools," the union's national coordinator, Rino Di Meglio, said in a statement.

There have been 27 incidents of aggression in schools this year, including teachers being stabbed, parents slapping principals and students throwing objects at teachers, according to the business daily il Sole 24 Ore. That is up from 36 all of last year.

The number included the stabbing of a 51-year-old teacher last May by a 16-year-old student at a public scientific high school in the Milan province, causing injuries to the shoulder, head and wrist.