For some definition of harming others.

The subtitle says:

if the student disrupts the class

And, in the body of the article:

The proposed law would allow teachers to physically intervene if a student harasses or insults others, or "significantly" disrupts lessons.

Did you?

The current legislation only allows teachers to use force if a student poses a danger to themselves, others, or school property. The teachers' union (Danmarks Lærerforening) has long called for greater flexibility, arguing that it is increasingly difficult to manage students who disturb class and refuse to keep quiet or leave when asked.

They already have the ability to restrain a child who is a danger to others, this is for children who are simply disrupting a class.