Young people should have to stay in education or training until they are 18, a think tank has said.
About 10% of 16 to 18-year-olds in Wales are not in work, education or training, according to the latest figures.
The Institute for Public Policy Research (IPPR) said letting children stop learning at 16 should be scrapped, to improve their prospects.
The Welsh Government said it had created 74,000 apprentices since 2016.
In Wales, children can leave school at the start of the summer term of the academic year they turn 16, but do not have to go on to further education or start training.
But in England, pupils have to study or train until they are 18, either going on to college or sixth form, an apprenticeship, or studying part-time while volunteering or working.
In the report, the IPPR said a similar, mandatory two-year learning requirement - which they call "skills participation" - in the classroom or work, should be introduced in Wales.
Russell Gunson, a director at the IPPR, said teenagers may be leaving school at 16 to start poor-quality careers, and those in work should be getting training at the same time.
"At the moment we're patting ourselves on the back for getting young people into jobs but without really checking whether those are high-quality jobs or not," he said.
"It's about making sure that all children in Wales have learning and training, though an apprenticeship, training if in the workplace, or through colleges, schools or universities if in the classroom."
"That way we can set up young people for good quality careers which sets Wales up for the future."
But he said changes in learning for young people needed to be accompanied by a major investment in adult learning.
Currently for every 100 people of working age, there are 33 pensioners, but this is forecast to increase to 40 by the end of the 2030s, the report said.
It also says the number of jobs at risk of being replaced by machines is 6.5% - this is higher in Wales than the UK average.
The think tank wants an extra £60m a year to fund an additional 30,000 adult learners by 2025, and an institute of technology to provide lifelong online and face-to-face training.
"That would take Wales up from a middling country in terms of the number of adults in education to among the highest in the world and that's the scale of the challenge we face," Mr Gunson said.
'I was clueless, but I learned a lot more'
When Jordan, from Cardiff, left school at 16, she was out of work for a few months and had nothing to do.
She wanted to become a carer, but with very little confidence she was worried about her future.
But then she joined a scheme run by the Prince's Trust, where young people get advice to gain skills and build their confidence.
"I was clueless," she said. "At the start I had no confidence, but I am so confident now."
Jordan, now 17, has taken part in cookery lessons, arts and craft, sports and adventure activities, and has returned to the classroom to study animal care.
"I think everyone should be in education until they are at least 18, because at 16 you are still a child," she said.
Mr Gunson said while things were going in the right direction, many of the reforms to skills and learning had been "baby steps" and there was a risk Wales would be left behind.
"What we need is to increase the scale of the choices the Welsh Government are making so the scale of the change meets the scale of the challenge," he said.
A Welsh Government spokesman said over 90% of learners continued in full-time education or training after the age of 16.
"We have a number of policies to help young people into work or education, including our investment in apprenticeships," he added.