Changes to the exam appeals process mean the education system now favours private-school pupils "more than ever before", according to deputy Labour leader Kezia Dugdale.

Ms Dugdale said that the introduction of charges for exam appeals last year has resulted in a drop in the number of appeals being lodged by pupils from state schools.

She said that appeals by state pupils have fallen by 55,000 since charging was brought in, a drop of 75% in one year.

Labour Freedom of Information requests showed that charges for state appeals were paid for by either the school or the local authority, Ms Dugdale said.

But private schools were giving parents the option to pay for appeals themselves.

The Labour deputy leader raised the issue as she questioned Nicola Sturgeon during First Minister's Questions at Holyrood.

"The truth is that the proportion of appeals from privately-educated pupils is now double that of state kids," Ms Dugdale said.

"The system now favours private-school pupils more than ever before.

"Parents of private-school pupils can buy their kids a second chance, parents of private-school pupils can put their hands in their pocket to help their kids, but state school pupils can't.

"It is no wonder that just the 220 kids from the poorest backgrounds in Scotland get the grades needed to make it to our top universities."

Ms Sturgeon said: "We have put in place a system that is right and proportionate in terms of appeals to give young people the best opportunity of fulfilling their potential at school."

She said 18-year-olds from the poorest backgrounds are now more likely to be accepted to university.

"Ucas stats show that the percentage of 18-year-olds from the most disadvantaged areas accepted to university is up from 6.4% under Labour to 8.9% in 2013," Ms Sturgeon said.

The First Minister said that in 2014 there had also been a record number of Higher passes in Scotland, almost 4,000 more than in 2013.

She added: "We are introducing... Curriculum for Excellence, and a new system of exams, and yes, changes to the way in which appeals are applied for and processed.

"We will continue to make sure that we continue to respond to the experience of all of that."

Ms Dugdale said Higher results could be the difference between getting a place at university or losing out.

"For disadvantaged kids, in particular, this can be a deal breaker," she added.

She also quizzed Ms Sturgeon on the news that almost half of pupils taking Highers this year will sit the existing exam and not the new qualification.

The new qualification is being introduced as part of the Curriculum for Excellence reforms.

Ms Dugdale asked: "What has gone wrong?"

Ms Sturgeon replied: "Nothing has gone wrong.

"What has happened is that teachers have been given the flexibility.

"Curriculum for Excellence is founded on professional judgement and I think it is right that decisions take account of local circumstances.

"Schools are able to use this flexibility to phase in the new qualifications in the way that best serves the interests of pupils.

"This flexibility was warmly welcomed when it was given by teacher unions and indeed by opposition politicians.

"This is the only year in which dual running of the exams will be permitted, but given the importance of ensuring proper implementation I would have thought that would have been something Kezia Dugdale and her colleagues would have welcomed."

Ms Dugdale said: "There is real concern from parents, teachers and pupils across Scotland, and we know that from the past when there is a problem in our education system, it is the kids from the poorest backgrounds who suffer the most."

Conservative leader Ruth Davidson accused the Scottish Government of "failing" on science and maths in schools and colleges.

Ms Davidson highlighted figures showing a reduction of student places on Stem (Science, Technology, Engineering and Maths) college courses.

She said: "When the SNP came to power there were over 86,000 college places in Stem subjects.

"The most recent figure is just 56,000 - a cut of 30,000 places in science, in technology, in engineering and in maths.

"This Government is failing on science and maths, because they are college courses that lead to jobs and they have been slashed by a third."

Ms Davidson also highlighted provisional figures showing that 65% of school pupils studying biology, chemistry and physics are expected to sit the current Higher exam compared to only 35% taking the new version.

She added: "In the international tables on every measurement since this Government came to power, Scotland has gone backwards in both science and in maths.

"Our young people need the skills to compete, getting a decent job depends on it. So why is this Government failing them?"

Ms Sturgeon said the most recent figures showed a 33% increase in students successfully completing courses leading to recognised qualifications while the average hours of learning per student had also risen.

She added: "We have, as we committed to doing in our manifesto, maintained the number of places in Scotland's colleges and the number of students achieving HNC/HNDs, which are qualifications both recognised and valued by employers, is up 36%.

"The number getting degrees is up 121%. I think that is something to be celebrated."

Ms Sturgeon said that more work was needed to get more girls and women to study Stem subjects.

She said: "I don't stand here and take the view that we have done everything we need to do, but we're doing the hard work to make sure that our colleges are equipped to give young people the preparation they need for the workplace and we will continue to focus on doing that."

The First Minister was also pressed by Labour MSP Mark Griffin on reports that science lessons in schools are being underfunded by £8 million per year, following the publication of research by the Learned Societies' Group on Scottish Science Education.

She said: "We continue to see a very strong picture on science in our schools, with increased higher entries across the three main science subjects since 2006, and pass rates remaining high.

"We do not agree that school science is underfunded."

Ms Sturgeon said the report had looked at about 2% of primary schools and 13% of secondary schools in reaching its conclusions.

"The report itself indicates that the findings should be treated with some caution," she said.