Southwest Preparatory Northwest Elementary School. In 1998, Southwest Preparatory School opened its doors to 23 students and today there are over 800. We have become the largest charter high school in Bexar County with four campuses located in the populated areas of the Northeast, Northwest and Southeast sections of San Antonio, Texas. If the past is any indication of what the future can be, then our growth and enviable record of success with at-risk students during the past 14 years will continue- as well our determination to provide educational opportunities to students through tuition-free public elementary, middle and high school.