In theory this is a simple problem in financial planning maths.
You can calculate how much you will need to be paying out, and when, and then you simply need to invest sufficient to provide the required sums.
In practice, if you can afford to save in advance, then you can probably afford to pay on a year-by-year basis out of income anyway.
If you can’t afford to save all of the cash needed in advance, then you save what you can and meet the shortfall from ordinary income.
If that isn’t enough, then the final option is to cover the last bit by raising a mortgage (or extending your present one).
As far as savings are concerned, there is rarely any requirement to set up anything specifically for the purpose – most people simply earmark some of their funds for the purpose.
If you do want to engage in specific planning, then your adviser might use a school fees package, but might just as easily use any of the wide selection of financial products and tools available to deliver the right plan for you.
The value of investments can fall as well as rise and you may not get back the amount you originally invested. Past performance is not a guide to future performance. Your property may be repossessed if you do not keep up repayments on your mortgage.