Try motivation. Pride in a job well done. Tell him/her it's a task for the future, promotion in the workplace, better remuneration for the professional attitude. Instil some enthusiasm for the project, (bring all the big guns into play), and if they say their schoolmates will take the mickey ask where will these schoolmates be in ten years' time when your offspring has a well paid career?
My three went to university because they were self-motivated. One's due to start her teacher training in September (a 2/1 and Masters under her belt), one's nearly finished his (ditto) and the third is halfway through a PhD in Physics. All three have foreign languages, French, German, Italian. The two younger ones live and work abroad in Europe. How's that for motivation?