She visited the Little Learners nursery in Edinburgh to back the Save the Children drive.
Pointing out that literacy and numeracy rates were falling under the SNP, Ruth said a policy based on the charity's Read On. Get On. campaign would be at the heart of the party's education policy.
It is estimated around one in five children from the poorest backgrounds leave primary school unable to read competently, yet another indication of Scotland's stubborn attainment gap.
The charity, which wants to achieve the target by 2025, has urged all parties to put the pledge at the heart of their Holyrood election manifestos.
Scottish Conservative leader Ruth Davidson said:
"We know that the attainment gap starts early - before children even reach primary - and widens throughout a child's school career.
"That's why it's essential we give all children the best possible start in life.
"The SNP has singularly failed to make any progress on narrowing the attainment gap, despite having sole control over education for almost a decade.
"It means almost as soon as a child enters Scotland's education system, their prospects are directly linked to the background they are from.
"That hits their chances for gaining key skills, entering further and higher education, and going onto to embark on the career they want.
"This campaign aims to have all children reading well by the age of 11 - that was a commitment in our gold standard education paper last year, and it will be in our manifesto too.
"Standards of literacy and numeracy in Scotland among young people have been allowed to slip - the Scottish Conservatives would place reversing that trend at the absolute heart of education policy.
"University may not be the choice of every child, but that doesn't mean every child shouldn't have the skills or the opportunity to attend."