The raft of offending against the boy began just after Cudby was released from prison for sexual offending against seven young girls.
In 1993 he was convicted of 12 charges representing indecencies against seven girls aged between seven and 10, committed between 1977 and 1993 when he was a school principal and sole charge teacher of a rural school. For that offending, he received a sentence of five years imprisonment.
Yesterday, the court heard how LTSA checks failed to identify Cudby's past and he got a job driving a school bus in the late 1990s.
Cudby said he had listed his sexual convictions on his application but somehow they were either ignored or had slipped through the cracks.
However, his past came to light after a member of the public recognised him as a known child sex offender. They were horrified he was driving a school bus and reported him.
The bus company immediately dismissed him, the court was told.
Justice Mallon said Cudby had groomed the boy from the time the child was six years old until he was aged 15.
The judge described the grooming as an aggravating factor, a huge breach of trust and repeating offending.
"It seems that you learned nothing from your earlier offending even though you received treatment in prison for your sexual offending."
Justice Mallon said Cudby simply could not stop himself.
"Apart from pleading guilty, there is nothing else that demonstrates any remorse at all.
"You were predatory and opportunistic... you have a very limited appreciation of your offending,"she said.
Cudby's age alone was not a mitigating factor, she said.
"So it's good that you pleaded guilty. Your sustained grooming of this boy has caused him serious harm. You have caused all these children serious harm."