Children are still "penalised" for being left-handed with ministers lacking the information to understand the scale of the problem, education campaigners have warned.
It is also feared a disproportionate number of prisoners are left-handed, with calls to research whether classroom struggles trigger a "downward spiral" in which pupils get low marks, their self-esteem drops and their future opportunities are damaged.
The Government has stood firm on the national curriculum despite campaigners asking for it to include a legal duty for left-handed pupils to receive specific teaching to meet their needs - something which is currently non-statutory guidance.
Education minister Nick Gibb, in a letter responding to concerns, said teachers need to ensure all pupils - including left-handers - receive "whatever specific support they require" to make progress and recognise which youngsters need extra help.
But handwriting experts and politicians believe there is a failure to recognise the difficulties encountered by left-handed youngsters which can hamper their development.
They believe many teachers are unaware about how to spot the signs while improvements to training would enable them to make simple but effective adjustments, such as a how a pupil holds a pen.
A Worcester-based alliance which has campaigned for more than 20 years and has involved - among others - MPs and Mark Stewart, who specialises in helping left-handed children improve their handwriting and offers training to teachers, has been left frustrated by a lack of progress in developing Government data and teacher training.
Former Conservative minister Sir Peter Luff, who is left-handed and was MP for Mid Worcestershire until 2015, told the Press Association: "This should be so easy to sort. It's of extreme importance and will cost nothing to address - not a penny.
"It takes a few strokes of the pen, a modest change to the teacher training syllabus and you are away.
"It's bizarre kids in our schools are penalised because they happen to be left-handed. It's bewildering successive governments have failed to act on this. It's so easy to do.
"It's about where you sit kids in class, how they hold their pen, it's really easy and nothing happens."
Mr Stewart, who runs Worcester-based Left 'n' Write with his wife Heather, told the Press Association: "In many cases there's no active help, there's a lack of teaching training.
"The Department for Education cannot speak with authority - it has no numbers on how many children are left-handed, no way of knowing if it has any impact on likely educational attainment."
The Department for Education does not record how many children are left-handed in the country's primary and secondary schools, stating this is because it is not considered a disability.
With around 10% of the population said to be left-handed, Mr Stewart has also written to the Government asking it to consider the specific impact on educational attainment.
He added: "I have heard there's a high percentage of the prison population is left-handed. One might think if the prison numbers are disproportionate, why is that the case?
"Early years education where children are struggling, making a mess of handwriting, they think this is a pain, no one knows how to sort it, they get low marks, low self-esteem, does it get in to a downward spiral?
"I appreciate that's a very long-term research project but clearly there's anecdotal evidence that getting help or not getting help can have a positive or detrimental effect."
Mr Stewart said he has helped thousands of children, with his talks to schools taking an hour and improvements to a child's pen grip being made within minutes.
He added: "When they are sorted, they are sorted for the rest of their life."
One primary school headteacher who received training from Mr Stewart said his staff were given a "wake-up call" about the need of "one of our hidden vulnerable groups - left-handed pupils".
A Department for Education spokesman said: "We trust teachers to provide support to children who are struggling for any reason."
The Ministry of Justice said it does not record how many prisoners are left-handed.