When I took German at secondary school, we were always told that 'möchten' would be preferable to 'wollen' here, as it is in similar languages such as English and Dutch. Perhaps in this case the students really want wine without asking for it politely, but in everyday situations, wouldn't 'wollen' be downright rude? Another instance at Duo is 'ich will zum Zoll, bitte', which sounds wrong to me. In English, for instance, I'd always say, 'I'd like to go to customs, please' and never 'I want', and similarly one would always say, 'I'd like wine, please' and never 'I want wine'. It's simply unacceptable in virtually all scenarios. I appreciate that the verb 'wollen' has to be introduced in some way, but is this really how Germans use this verb?
"Wollen" simply means "want." You can use it with a noun ("Die Studenten wollen Wein"-- "The students want wine") or with a verb as an infinitive ("Die Studenten wollen Wein trinken"-- "The students want to drink wine"). The "to" comes with the infinitive verb ("trinken," "to drink" in my example), so "wollen" simply translates to "will."