As a mother whos DS has been excluded for throwing a chair across the class room, I can see her point.
DS school refused, and at one point would do anything to be sent home from school. A couple of days at home with mum? Brilliant! He didn't notice that I spent the day in tears and in despair, wondering how I could possibly have a child who has been excluded.
IMO, the boy should have been collected from school immediately, or preferably given some cool off time, supervised one to one until the end of the day, and then had in internal exclusions. This does take up one whole member of staff though, and you can't just leave a child like this sitting with the secretary, they need a member of staff who is trained in dealing challenging behaviour.
He certainly should NOT have returned to class that day. It's not fair on the teacher or the other children.
We have a brilliant head at the school at them moment, and she wouldn't hesitate in excluding a child for this behaviour, but she would explain to the child why they are being excluded, and would have it followed up with an assessment/meeting with the ed spych.
The child is 7, you say? I really hope the school and his family can help him through this.