The number of disciplines where the ACT scored the highest mean score in NAPLAN has fallen.
In seven of the 20 domains tested, the ACT scored the highest average, or equal highest, of the states and territories.
This is down from nine last year.
Victorian students pipped those in the ACT as the state gained the top mark in eight domains.
But the ACT government said that in 18 or the 20 measures, the territory's scores were close to or not statistically different to other states when considering the margin of error.
Canberra students were better represented in the top performance bands than in the previous test, according to the final release of 2019 results from Australian Curriculum Assessment and Reporting Authority.
Students scored above the national average in the top performance bands in 14 of the 20 domains, opposed to 2018 where it was only seven.
In May, students in years 3, 5, 7 and 9 are tested across five disciplines - reading, writing, spelling, grammar and punctuation and numeracy.
Overall, ACT students performed well, scoring above the national average in most of the year levels and disciplines.
It was only year 3 students who fell below the national average in writing and spelling. Year 5 students also scored below average in spelling.
Each year level also topped the nation in reading.
High school students performed better than primary school students in Canberra, with year 9 students coming out on top.
Year 9 students were best represented in the highest performance rankings. In three disciplines - reading, writing and grammar and punctuation - ACT year 9 students had the highest percentage of students, compared with other jurisdictions, to score in band 10 or above.
In reading, spelling and punctuation year 9 students came out on top.
But despite leading the nation in reading, the number of year 9 students to achieve a result above the national minimum standard dropped substantially on 2018 results.
Almost 7 per cent of year 9 students in Canberra fell below the minimum standard, in the prior year only 3 per cent of students scored below the standard.
The results also showed a slight uptick in writing performance.
Based on 2018 results, the Productivity Commission report found 11.2 per cent of year students failed to reach the standard for writing and more than 16 per cent of year 9's.
The 2019 results showed a slight improvement for both year 7 and year 9 students.
In year 7, 10 per cent of students did not meet the minimum standard for writing and 14.8 per cent of year 9 students fell below.
The improvement in writing results was seen across the board ACARA chief executive David de Carvalho said.
"NAPLAN has enabled a spotlight to be focused on writing, and what teachers are doing seems to be making a difference," he said.
"Hopefully, this first year of turnaround will be the beginning of a trend.
"The writing results overall, however, are still below where they were when writing was first tested, with the exception of year 3."
Female students in Canberra outperformed males in every year group across the literacy disciplines but males performed better in each year level for numeracy.
Those in the ACT with a language background other than English scored better in 13 of the domains.
ACARA's report is not adjusted for socioeconomic advantage. Previous independent reports have found students lagged behind those from similar socioeconomic backgrounds interstate.
This article has been updated since it was first published.