The 56-year-old, who pleaded guilty to 10 charges related to the attack including three counts of sexual intercourse with a child under 10, was sentenced in Downing Centre District Court on Wednesday.

Sampieri also admitted charges related to sexually explicit and harassing phone calls he made to women in the months before the Kogarah attack.

In handing down his sentence, Acting Judge Paul Conlon said he agreed with the Crown that the November 2018 attack can "only be described as any parent's worst nightmare".

He sentenced Sampieri to life in jail with no non-parole period.

Sampieri - on parole at the time for a rape in Wollongong - raped, punched and bound the seven-year-old in the toilets after consuming the drug ice.

The court heard the girl was detained for up to 50 minutes and Judge Conlon said it would have been "terrifying" for the victim, who would have had "grave fears" for her safety.

"The offender demonstrated a callous disregard for the child," he said.

Judge Conlon added that Sampieri subjected the young girl to sexual abuse of the "most horrifying and degrading kind".

Sampieri had admitted he said he was in such a state of sexual excitement by the time he was in the dance studio facility, he would have attacked anyone who had walked in.

"Using crystal meth, I believe that led me to what I did," Sampieri told a sentence hearing last week.

Judge Conlon described mechanic Nick Gilio as brave for confronting the knife-wielding Sampieri after he found the girl in the toilets after the attack. Gilio suffered several large cuts to the back of his head, neck and abdomen.

"The victim, the family ... the whole community are indebted to the courage you displayed," he said.

Australian Associated Press