Classes in pediatrics are offered in Medical school. You need to get an undergraduate degree before attending medical school. To become a Pediatrician, you need four years as an undergraduate, four years as a medical student and then at least three years as a medical intern and resident.
It is difficult to get into medical school. The quality of your undergraduate education is extremely important in getting into one. With the exception of Catholic Universities (e.g., Notre Dame, Georgetown, Boston College, Villanova), most Christian colleges are not very good academically. That means that going to a Non-Catholic Christian College will probably make it very difficult to get into a medical school once you graduate. There are a few other schools with a church affiliation (e.g., SMU, Brigham Young) that have decent academic records. But anything that calls itself a Bible College or a Christian College (without specifying a denomination) (e.g., Bethel College, Liberty College) is unlikely to be a good enough school to get you into a good medical school. You can ask admissions offices how many of their graduates get into medical schools each year.