Entity Framework Core: Update relation with Id only without extra call

I'm trying to figure out how to deal with 'Single navigation property case' described in this doc:

Let's say we have 2 models.

class School
{
   public ICollection<Child> Childrens {get; set;}
   ...
}

and

class Child
{
    public int Id {get; set;}
    ...
}

So it's many-to-one relationship created by convention, without explicit foreign key in a Child.

So the question is if we have Child instance and know School.Id is there a way to update this relation without extra call to database to obtain School instance.