I actually think this is a good idea.
It SHOULD be the parents giving their kids a balanced diet in the first place.
The only problem I foresee is that if the kids don't get fed junk at school, they will get sweets etc after school, or the ritualistic trip to McDonald's.
It is great to see some power being administered by teachers to confiscate such things - no doubt we will hear parents complain it is against the 'human rights' of the child.
When I was at school (11 years ago), you would have chocolates and sweets wrenched off you if you were munching while walking down the corridor.
A good move I think - but I cannot see it lasting, nor having much effect against parents determined to take the fast-food option.
***EDIT:- Fellbuddy below makes an excellent point about the school being in 'Loco Parentis' while the child is at school. Does the school not have a responsibility to do what they believe is best for the children while they are in the care of the school?
When you submit children to a school, you are entering into the 'Loco Parentis' rule, as seen on all school trip forms etc (well at least it was when I was at school).
If children were bringing in something or doing an activity detrimental to their wellbeing - would we not be up in arms if the teachers did not intervene?