In any case, a jacket should be water-repellent and waterproof. Especially in the autumn and winter months, we have very high humidity in addition to fog, rain and snow.
The outer material should be windproof, the zips should have a cover, pockets should be covered and it should be possible to close the hood tightly. Children in particular like to be outside longer in the winter when it snows, and the jacket should insulate them sufficiently.
Breathability is important, but so is the cut and the length and texture of the sleeves. A child's winter jacket should not be too tight or too loose. If it is too tight, there is only an insufficient air cushion which actually provides warmth. Wide jackets also do not build up insulation.
The sleeves should have cuffs or Velcro fasteners to prevent cold air from entering. The wrist should be covered by the sleeves. The ends of the sleeves should have cuffs or a ribbed hem.