Massachusetts is one of a growing number of states that are putting new restrictions on the practice of restraining and secluding public school students.

The techniques — which have been blamed for harming students and in at least 20 deaths — were used more than 267,000 times in a recent school year, according to an analysis last year of federal data by NPR and ProPublica.

Starting this year, Massachusetts will no longer allow school staff to pin students face-down on the floor, except in rare circumstances when a doctor approves it for a specific student, ProPublica reports.

Restraint and seclusion are supposed to be used in extraordinary circumstances, when a child's behavior puts himself or others at risk. But federal officials have expressed concern that restraint and seclusion are overused and have sought to limit it.

One result is that many states, like Massachusetts, have reformed their use of the practice. Research by Jessica Butler, an attorney and mother of a child with autism, finds 32 states now "provide some meaningful protections against both restraint and seclusion for children with disabilities." Butler's 2014 report, for the Autism National Committee, included Massachusetts in that count. But a state official told ProPublica that its rules were "long overdue for a very serious and thorough review."

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