In cases such as these, a picture really does speak a thousand words. so if you could update your post with images then that would be really great. Generally, white spots are the result of some sort of plant pest such as bacteria, fungi or insects. There is a possibility that the spots are caused by something else, such as a nutrient deficiency but there would be other symptoms too - such as stunted growth of the plants.
As has already been mentioned, the spots could be caused by flea beetle damage. Look for tiny jumping insects in the plants. Try brushing your hand over the leaves to look for them jumping, or look for other any other insects that could be the culprit.
In terms of diseases, kale can be attacked by Cercospora fungi which can cause circular white spots on the foliage which may join together to form larger blotches. The disease is called white leaf spot and is not listed in the pest and disease section as it is not usually an important disease of kale. It is usually more severe on related turnip and mustard, but that's not to say your plants are not infected with it. Here is the link to a factsheet which describes the disease http://pods.dasnr.okstate.edu/docusha...
Please do add the images so we can help further, it's also a good idea to add your location to your profile