By comparison, that is nearly eight times the £53,000 average debt students leave university with in England. It is also well over twice the average pension pot for 65 to 74-year-olds, which is £145,900 according to the latest available figures from the Office for National Statistics.

JISAs are tax-free savings or investment accounts for children under the age of 18, with an annual allowance of up to £9,000. On the account holder’s 18th birthday, the JISA converts into an adult ISA and they are given full access.

Reaching £397,500 in the past 18 years based on maximising the annual allowances for JISAs and Child Trust Funds (CTFs), their predecessors, would have required an incredible average annual return of just over 21%, Murphy Wealth’s figures suggest.

The MSCI All Country World Index has averaged a return of 10.82% since 1988, meaning the top JISA accounts have performed nearly twice as well as the market. Between 2015 and 2025, the average cash ISA has delivered an average return of 1.21%.

The annual contribution limit for CTFs was £1,200 until they were replaced by JISAs in 2011. After starting out at £3,600, the allowance for JISAs has been £9,000 since the 202/21 tax year.

A separate FoI from Murphy Wealth earlier this year found that the number of maximised JISAs reached the highest point since the pandemic during 2023/24 – the most recent tax year available – at 78,330.

Of those accounts, 61,881 were invested in stocks and shares and the remaining 16,461 were cash – meaning nearly 80% of the maximised accounts were invested. In total, there were 770,000 cash and 598,000 stocks and shares JISAs, statistics from HMRC show, indicating more than 10% of the latter are maximised compared to 2% of cash accounts.

Adrian Murphy, CEO of Murphy Wealth, said: “Receiving nearly £400,000 on your 18th birthday would set you up nicely for adult life. You wouldn’t have to take on student debt to pay yourself through university; you could put at least a sizeable deposit on a property in the vast majority of the country, with cash to spare; or let it roll over into an adult ISA and likely become a millionaire by the time you are 30.

“For those able to do so, it underlines the power of saving as early as possible on your children’s behalf and the power of compounding over time. There is no way you could get anywhere near those figures through cash – every penny put in these accounts must have been invested over the course of 18 years.

“The fact that such a large percentage of the maximised accounts are in stocks and shares shows that more people are beginning to understand the difference investing can make. While markets go through periods of volatility, like they are right now with the conflict in the Middle East, they have bounced back and gone on far superior returns to cash over most timeframes.

“With pensions becoming part of people’s estates from next year, making use of JISAs is a great way to tax efficiently pass down wealth. Junior SIPPs are another option, but the annual contribution limit is much lower at £2,880 and the recipient can’t access the money until they are close to retirement, which does little to help them out as they navigate becoming an adult.

“Passing down wealth to family members can be a complex and long-term process, so it’s important you have a plan and don’t leave yourself short. Speak to a financial adviser who can provide guidance on how to sustainably gift money to children and grandchildren, while ensuring your financial requirements are taken care of in retirement.”