The way I do it is parents provide milk for their kids by bringing in full bottles/ sippys in the morning. I send the bottles back at night for them to clean. So I really don't care if they are using a bottle or sippy. However the feeding on the back thing would bother me because I only serve milk at mealtimes in their high hair. I give it to them AFTER they are done eating because kids this age should be getting most of their calories from food not milk.