In middle and high school, you should concentrate on math and science classes, especially biology, to prepare for the courses you will be taking in college. And because veterinary schools are even more selective than medical schools, you should make sure you do well in all of your courses.
The school you go to determines what courses you need to take for your pre-veterinary studies, but you do not have to complete an official pre-veterinary program. The required courses will have a strong scientific and mathematical curriculum, but you will also have to take courses in social studies and humanities. You may also need to show proficiency in a foreign language. For example, North Carolina State University requires applicants complete animal nutrition, biochemistry, biology/zoology, calculus or logic, general chemistry, organic chemistry, English composition, genetics, humanities, social sciences, microbiology, physics and statistics. Lab work is also required in many of the science courses.
If you want to find out the specific requirements of an individual school, start at the Web site for the Association of American Veterinary Medical Colleges. Click "Applying to Veterinary School" and then "College Specific Requirements." You can then choose the schools that you are interested in from the list.