I travelled to Norway a month ago, and whilst there I noticed that all the school children wore red jumpsuits. I thought that this seemed quite distinctive and wondered why this was - perhaps it is more practical in the cold weather?
A month ago would have been the time of Russefeiring.
The russefeiring traditionally starts on around 20 April and ends on 17 May, the Norwegian Constitution day. Participants wear coloured overalls, they make groups and name a bus, car or van and celebrate almost continually during this period.
There are several different types of russ differing in the colour of the caps and traditional uniforms most students carry during the entire russ period. The colour of the uniforms usually reflects what type of study the person is completing. However, in some regions such as Stavanger, the colour is determined by the school. Typically in these areas, if the headmaster of the school was a blue russ, the students will also be blue regardless of what they are studying.
So this is a special celebration, not an all-year uniform. Only those graduating high school (18 years old) take part, and some students will be wearing colours other than red. The colour may indicate the area of study, or the school.
This may be the wrong answer, but if it is a bright red, it could be the same reason German schoolchildren are wearing high-visibility jackets on excursions:
While unusual 10 years before, it is now a normal sight in Germany. Because children are often spontanous and impulsive, they could do some dangerous tomfoolery even under supervision. It also helps to see if one is falling back behind the group and as car driver you really see them miles away.