Don't know about New Zealand, but in the United States, any law student who agreed to do this would probably not be worth the money you paid. I don't think any state permits law students to practice the law, and every student knows that. There are some exceptions, but the only ones I know of involve work for the government or nonprofits, and still require supervision by a real lawyer. Doing this would be a great way for the student to ensure that he is not admitted to practice upon graduation.
Fiddling with the wording wouldn't get you any further, either, because the bodies that regulate lawyers take a very broad view of what it means to practice law, The wording you've selected is particularly inadequate, because practicing law is sometimes even defined as "providing legal services." But even if your contract referred to it as "sensual massage" services, the courts are going to look to the substance of the services provided, not the name. And the services you're describing -- appearing at hearings, arguing on your behalf, presenting evidence -- are very classic lawyer activities.
As soon as the student was revealed as a student to the court, the judge would eject him and report him for misconduct.
I believe I have seen some weird situations, though, where a person goes into court, represents himself, and then recovers his expenses. So what I could imagine is a case where a person like that also recovers for an amount paid to a student for more limited services like research and writing.
Still, it would be really risky for the student, because that would still be considered practicing without a license and would really jam him up. The litigant would probably not get in trouble, though I could imagine a judge refusing to award that portion of fees if he found out about the student's involvement.