Experienced apprentice Stephanie Lacey faces a stiff challenge to help Queensland secure a first National Apprentices Challenge in the last heat on Wednesday.
Queensland lead on 18 points, one in front of South Australia and three ahead of Victoria after four heats.
The series was first run in 2008 and since then South Australia have won it five times, Victoria twice, West Australia twice and NSW once.
Lacey, who has ridden 136 career winners, has drawn the Chris Waller trained Andaz – one of four horses under $5 for the race at Sandown.
Queensland jockey coach Shane Scriven said the series had been one of the most keenly contested and exciting on record.
“But the main thing it has given young riders a chance to compete at different venues and see how racing is run in different parts of the country,” he said.