This is difficult one as it depends upon the interpretation of the order. It is generally considered that higher education or tertiary education means a first degree not a second or third one. Equally if someone ceases education and gets a full time job that terminates the maintenance obligation. So in my view no you cannot be required to resume payments for your second son because he has ceased education and chosen voluntarily to resume it. I also do not consider that you are obliged to pay for your son taking a masters degree. At the end of the day you amy have to take it back to court but I cannot see a court sanctioning maintenance for an adult child who chooses to be an indefinite student. You are stuck with paying your ex however until your third son finishes university if he is going there unless you want to apply to court for a variation.