Cash from a fund aimed at helping close the attainment gap in schools was used to send pupils and their parents on a weekend trip away, the First Minister has revealed.
However, she said using Pupil Equity Fund money for that had helped improve attendance rates.
She gave the example as she was pressed by Scottish Conservative leader Ruth Davidson on the Government's efforts to close the attainment gap - with the Tory claiming cash was either lying unspent or was being used by schools to help with "plugging gaps left by budget cuts or to pay for other costs like campus police, staff bonuses and installing an astroturf pitch".
Raising the issue at First Minister's Questions, the Tory MSP said: "That is all well and good but it is hardly closing the attainment gap."
Ms Davidson demanded the First Minister "give me an assurance today that taxpayers' money intended to help poorer pupils will do just that and stop being siphoned off elsewhere".
The £120 million Pupil Equity Fund sees cash given directly to head teachers for them to determine how it should be spent, with the scheme part of Scottish Government efforts to tackle the gap in performance between rich pupils and more deprived youngsters.
Ms Sturgeon said money was allocated to "some things that at first glance many people would think 'is that appropriate in terms of raising attainment?'".
She stressed, though, that it went on measures that "head teachers say help raise attainment in their schools".
She added: "I was at a school recently where one of the things they did was take some pupils and parents where attendance had been an issue on a weekend trip and attendance has improved because of that amongst some of the most deprived communities."
The First Minister said: "She says there is widespread concerns across the sector about the Pupil Equity Fund, frankly I think Ruth Davidson needs to get out a bit more and visit a few more schools, because when I visit schools what I hear about the Pupil Equity Fund is it is the single most important thing that is happening right now in raising attainment in our schools."
Ms Davidson also raised concerns about the £750 million Attainment Scotland Fund established by ministers to tackle the problem.
The Conservative said: "Millions of pounds from that fund, which is intended to drive up the performance of poor pupils, is still lying unspent because of difficulties in recruiting.
"In other words, money that should be spent on cutting the attainment gap now is instead lying in the Government's bank account because they can't find the teachers to spend it on."
The SNP leader, however, said Ms Davidson's questions "display a fundamental misunderstanding of the funding behind the attainment programme".
The First Minister said: "It's a £750 million commitment across this entire Parliament so any money not spent in one year rolls forward to the next year and every single penny, of course, will be spent on measures to reduce that attainment gap.
"In the early years of a programme while plans are being put in place - and, yes, while recruitment of extra staff is taking place - there will obviously be less money spent than there will be in later years of that programme."
She insisted that "every single penny" from the fund would go towards closing the attainment gap - something which Ms Sturgeon has said is her number one priority.