Source: ABC News 

Healdton Public School District in Oklahoma, south central US, has installed seven bulletproof shelters inside its elementary school classrooms and another two in its middle school, after the deadly mass shooting at a Florida high school that claimed 17 lives recently.

Each shelter can accommodate up to 35 students and 2 teachers, with an area of about 5.8 square meters. The principal reportedly has personally tested the shelter.

(Compiled by Shan Xin)