Are school doors bulletproof?

The vast majority of standard entry and interior classroom doors installed in older school buildings throughout the United States are not naturally bulletproof. Standard school doors are typically constructed from standard hollow metal or solid-core wood materials, which can provide basic structural security and fire resistance but cannot stop high-velocity ballistic rounds. However, in response to modern active shooter concerns, many school districts are actively upgrading their security postures. This is achieved by installing specialized, certified ballistic-rated security doors that meet rigorous Underwriters Laboratories (UL 752) safety standards. Alternatively, because completely replacing doors is highly expensive, many schools utilize cost-effective retrofits, such as applying heavy-duty anti-ballistic armor panels inside the existing doors or installing thick, shatter-resistant security window films over the door's glass lites to prevent forced entry.