ADELAIDE, April 21 - Tivendale School principal Lisa Coon, who has held a range of roles in the Don Dale centre since the 1990s, has told the royal commission into the Northern Territory's juvenile justice system that when it opened it was "akin to a hotel in many aspects".

She says both the physical centre and the nature of its young detainees have changed since then, with detainees now more likely to be "bigger" and facing longer sentences.