Any money left to a minor is automatically placed 'upon trust' until the child becomes an adult (at the age of 18). That occurs even if the will makes no specific reference to such a trust but a well-drafted will should always make clear
(a) who the trustees are to be ; and
(b) the purposes for which those trustees can use the money (or any income generated by it) prior to the beneficiaries becoming adults (such as for their education).
It's possible to extend the period before a trust comes to an end (e.g. to the age of 21) but doing so can create difficulties and you'd need to seek expert advice in order to get it right.