Some people are not breakfast eaters. You tend to learn which meals the children eat the most, some at breakfast, some at lunch and some at afternoon snack in my daycare. I have learned to serve small portions and offer seconds at all meals. All children go through phases where they won't eat anything and then all of a sudden you can't fill them up while they have a growth spurt.
If they are hungry they will eat. The important thing is to offer the food at every meal even if it is just a couple teaspoons of everything. That's what I do when I have a child who won't eat because that way I'm not angry about throwing all the food in the garbage. I went through that last year with one child.