The proportion of 11-year-olds in England reaching the standard expected of them in reading and maths has risen by 3% and 4% respectively, official figures show.
The percentage of pupils achieving the expected level, level 4 or above, in the national curriculum or Sats reading tests, increased from 84% last year to 87% this year, the Department for Education (DfE) said.
The number reaching the same level in the maths test rose from 80% to 84%.
Arrangements for the writing test have changed this year, meaning it is not comparable to previous years, but the overall figure for those who have reached level 4 in English - reading and writing - is regarded as 85%, the DfE said.
The proportion of pupils achieving above the expected level, level 5 or above, rose in the reading tests from 43% to 48%, and in maths from 35% to 39%. In the reading tests, girls have historically performed better than boys, and this year 90% of girls and 84% of boys achieved level 4 or above. Boys' improvement was more pronounced, up 3% over the previous year compared to an increase of 2% for girls.
In maths, there were similar levels of achievement for both boys and girls.
The arrangements for writing tests changed. This year, schools were no longer required to administer a writing test and submit it for external marking. As a result, measures based on teacher assessments were introduced for the first time. This year's figures for English cannot be compared to the figures for English that were published in earlier years, which were based solely on tests.
Pupils are expected to make two levels of progress between Key Stage 1 and this stage, Key Stage 2. The proportion of pupils in state-funded schools making the expected progress was 89% in English, a figure not comparable with previous years, and 87% in maths, up from 83% last year.
The proportion of pupils achieving the expected level this year, based on teacher assessment of writing tests, was 81%. The equivalent figure in 2011, based on writing test results, was 75%.
A DfE spokesman said: "There is evidence to support a real increase in the percentage of pupils achieving the expected level this year. However, as no information on writing teacher assessment is available for previous years and the writing sample test results are not directly comparable to test arrangements in previous years, the evidence for a real increase in attainment in writing is less strong."