The teachers and staff are beyond exceptional. The Keystone School is an online high school and middle school offering flexible and engaging school programs open for enrollment year round. Students are eager to learn and treat each other and staff with respect and kindness. Discover all the facts about Keystone School and its 436 students, including 36 ratings & reviews; view test scores and nearby houses. Keystone offers over 120 online high school and middle school courses all supported by certified teachers. Look for your teacher/course on RateMyTeachers.com working at Keystone School located in San Antonio, Texas, United States Private School in San Antonio, TX. Keystone School in San Antonio, Texas serves 491 students in grades Nursery/Preschool-12. This organization is not BBB accredited. I took AP Statistics through Keystone because the course would not fit in my schedule in my high school. Students can enroll full-time to earn an accredited online high school diploma or part-time to supplement a Continue reading » Keystone School, generally called Keystone, is a co-educational independent private school for pre-kindergarten, elementary school, middle school and high school located in the Monte Vista Historic District in Midtown San Antonio, Texas. I'm leaving because I'm relocating after getting married. Original review: Oct. 21, 2019. Keystone School in San Antonio is one of the best schools in the state. See BBB rating, reviews, complaints, & more. View their 2020 profile to find tuition cost, acceptance rates, reviews and more. I was hired as a substitute teacher and found a regular position as an Administrative Assistant.