One of the charities that I support is the Animal Welfare Institute. This organization and others provide plenty of evidence that large numbers of animals are subject to unnecessary cruelty, primarily in order to reduce the cost of feeding our growing population. This situation will only improve when more people become aware of the way that animals are actually raised and killed.
In the short term, I think it would be good if high schools conducted field trips to slaughterhouses so that kids around the age of 16 could see where their food comes from. In the long term, I hope we figure out how to create artifical meat on a large scale so that we don't need to kill animals for food in the first place.