The education secretary made a statement to the Scottish Parliament this afternoon after the latest Scottish Survey for Literacy and Numeracy found writing performance of youngsters in the second year of secondary and the final year of primary fell between 2016 and 2012.
Mr Swinney told the chamber the figures were not good enough and said there were several key areas where education must improve.
He said there was a need to get better at tracking the progress of each individual pupil over the course of their school career, as well as a need to be clearer about standards expected in classrooms.
Mr Swinney said the Scottish Government had already taken action on educational reform but added that it would not deliver “an overnight solution, it will take time before we see their full effect”.
He said: “It is clear we must stay the course and continue to make the changes that are necessary to strengthen Scottish education.
“This requires an unwavering focus on improving Scotland’s education system for every child and we are doing exactly that.”
Scottish Conservatives spokeswoman Liz Smith said many parents in Scotland would view the statistics as “shameful”.
Iain Gray of Labour said class sizes north of the border had grown to some of “the biggest in the developed world” and called for more teachers “with more support to do the job they love to do.”