Consumer expert Martin Lewis says 60% of schools still do not teach children about financial education - leaving many open to scams.
Speaking on the ITV Money Show on Thursday, Lewis visited the secondary Hendon School, while co-host Angellica Bell visited Cheam Park Farm primary school.
Both schools have specialities in teaching about money, but Lewis said this is far from the norm.
"The truth is 60% of schools not not teach any financial education at all," Lewis said.
Speaking to Hendon School head of maths Esa Roman, Lewis said: "We have a massive problem with financial capability across the nation. We leave them in the mire without teachers like you."
Children at the school were taught about how to spot a financial scam advert online.
Some kids said adverts featuring Lewis were most likely to be legitimate - but the opposite is true, as he has never advertised a financial product.
Lewis said: "If you ever see an advert with me in it, it's a lie. Whenever you are on the internet, you have to have someone on your back whispering in your ear saying: 'is this real?'."
The class was also taught about the value of saving.
Lewis said: "Saving is putting spare money aside each month and the bank gives you interest so you can buy something you need later.
"Debt is buying something now and then paying the bank each month.
"When you save, they pay you. When you borrow, you pay them. In the long term, it's cheaper to save and buy than borrow and buy, but it is more difficult. You have to plan it a bit better."
Parents who want to give their children an overview of personal finance can download a free textbook, funded by Lewis.
The book, Your Money Matters has been designed for use with young people age 14 – 16 and covers topics including spending and saving, borrowing, debt, insurance, student finance and future planning.
You can download the England version here, the Scottish one here, the Northern Ireland one here and the Welsh one here.
In July a Martin Lewis-backed report said UK schoolchildren should be taught basic money skills in primary schools by 2030.
The report in question was created by the APPG (All Party Parliamentary Group) regarding Financial Education for Young People.
It found a lack of good money education puts young people at risk of fraud, debt and financial abuse.
It asked the government to set a target in order for primary school children to have access to a financial education alongside the investment and willing needed to make this happen.
While the APPG can raise awareness of such an issue it does not have the direct power to pass laws itself.
The APPG is made up of 150 MPs and peers from different parties.
