The Trump administration has surreptitiously altered federal government websites dealing with juvenile justice to remove the ambition that American children should be “healthy and educated”.

The change was among a raft of revisions quietly imposed on public information websites by a little-known agency of the justice department known as the Office of Juvenile Justice and Delinquency Prevention (OJJDP). It advises states and local communities on how to treat minors in trouble with the law.

Under the agency’s old vision statement, the office expressed a desire for America to be “a nation where our children are healthy, educated, and free from violence”.

After Donald Trump entered the White House in January 2017, the phrase was changed – without any public notice or consultation – to “a nation where our children are free from crime and violence”.

Other changes to the agency’s websites included removing guidance that urged states to stop putting children into solitary confinement, avoid placing girls behind bars and address the disproportionate impact of courts and prisons on black and other minority kids.

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The unannounced alterations were spotted by the open information group the Sunlight Foundation. Its Web Integrity Project, which monitors tens of thousands of government websites, became aware of a large number of edits being made to the agency’s web output.

Researchers at the project used the Wayback Machine, which archives billions of internet pages, to compare today’s web pages with pre-Trump offerings. The findings suggest that under new leadership the juvenile justice branch of the Department of Justice has begun to change its messaging in order to reflect a tougher federal approach to children that emphasizes punishment over rehabilitation.

The change in approach followed the appointment by Trump of Caren Harp as head of the DoJ’s juvenile justice agency. Harp has a track record as both a prosecutor and defender, and before taking over the helm in January was associate law professor at Liberty University, a Christian institution in Virginia with ties to the conservative movement.

In an interview published with a juvenile justice magazine in March, Harp said that in her view the system had become imbalanced and she urged a return to a more penal approach. “There’s a need to return to balanced consideration of public safety, offender accountability and youth development.”

She added: “It drifted a bit to a focus on avoiding arrests at all costs and therapeutic intervention. It went a little too far to the side of providing services without thinking of short-term safety.”

The Marshall Project reported last month that under Harp the agency has quietly dropped a number of important research projects designed to assist states in reducing the disproportionate imprisonment of black and other minority young people. The attorney general, Jeff Sessions, a former US senator from Alabama, had pressed for the changes, complaining of unnecessary regulation.

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In a statement released to the Guardian, a spokesman for the juvenile justice agency said that the changes to its websites were part of a “normal transition from one administration to another. Web pages are removed or archived in order to review content and ensure programs, policy and other online information is current.”

The Sunlight Foundation discovered a number of notable alterations that the agency has made without alerting anybody. It has radically revised the language it uses to describe children who get caught up in the criminal justice system from the neutral, albeit clunky “justice-involved youth” to the more judgmental “offender”.

It has also removed a page called Girls and the Juvenile Justice System that gave girls and young women advice on how to relate to the criminal justice system. The expunged page noted that girls’ share of arrests, custody and court appearances have increased steadily over the past 30 years to almost a third of juvenile cases.

It added that girls who become trapped in the system are “often girls of color and girls living in poverty. They are typically nonviolent and pose little or no risk to public safety. Their involvement with the juvenile justice system usually does more harm than good.”

The agency has also scrapped a page called “Eliminating solitary confinement for youth”. It urged states and local communities to stop placing kids into isolation cells as an “important step toward improving conditions and creating an environment where they can heal and thrive”.