The US has been rocked by more than 900 incidents involving gunfire on school grounds in the last 10 years, Joe Biden has said.
On Tuesday, Texas was hit by the deadliest school shooting for a decade when a teenager opened fire at a primary school, killing at least 21 people including 19 children.
Until the massacre at Colorado's Columbine High School in 1999, death tolls tended to be in the single digits.
Since then, the number of school shootings where 10 or more have been killed has mounted..
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