Victorian students are falling behind the rest of the country in the rate of improvement made by students, according to an analysis of the latest NAPLAN data.

Education consultant and mathematician Russell Boyle has used the data to compile a "Value Added Learning" (VAL) index, which compares the improvement made by students in each state and territory across any or all of the five NAPLAN scales. The index found Victoria was behind the national figure on all but two of the 10 categories.

Worst were primary grammar and punctuation, which rated 119.6 on the VAL index, compared with the national figure of 123.9, and primary numeracy, which rated 120.6, against a national figure of 123.1.

Victoria's primary reading rated 119.6 - compared with a national figure of 121.7.

But secondary reading rated 107.2 - higher than the national figure of 106.9 - and secondary numeracy rated 107.3 - equal to the national figure.

Mr Boyle said the figures showed Victorian schools needed to spend more time teaching core subjects.

“While Victoria may be doing well in absolute terms, with high mean scaled scores, it is performing poorly in terms of the value it adds to student learning from year 3 to year 5 in primary schools and between year 7 and year 9 at the secondary level," he said.

“NAPLAN is a relative rather than an absolute exercise. Its raison d'etre is to lift standards by challenging students and schools to improve. In Victoria, we need to place a greater emphasis and spend more time on reading, writing, spelling, grammar, punctuation and numeracy."

On average, primary schools across Australia improved the numeracy performance of their students by 23.1 per cent between year 3 in 2008 and year 5 in 2010.

Victoria's primary school students improved their numeracy skills by 20.6 per cent. Queensland students improved the most, with a 28.7 per cent improvement across the two years.

At 105.4, the writing VAL for Victoria's secondary schools is less than the VAL index for all Australian secondary schools of 106.4. Victoria's students improved their writing skills by 5.4 per cent between year 7 in 2008 and year 9 in 2010.