What major would be ideal for learning and concentrating on genetic engineering. The topics I am interested range from environmental to medical aspects.
In addition, are there any schools that specialize in this?
Genetic engineering is a part of molecular biology/cell biology/biochemistry.
A number of majors could be appropriate for your interest in genetic engineering. As mentioned above, molecular biology/cell biology/biochemistry would be appropriate majors. You also could consider majors in genetics, biotechnology, or microbiology. Don’t overlook the genetics options in colleges of agriculture, too. (Sometimes, these are offered in a broader field, such as plant science.) Depending on your specific interests and the particular departments that interest you, you might find some relevant aspects of genetic engineering in nanotechnology or biological engineering programs (sometimes combined in a chemical engineering dep and sometimes in an ag engineering dept.)