The following link indicates that you need to apply with the Italian Consulate prior to your departure. I would apply with the Italian Consulate. I hope this answers your question. If not, then please reply. Thank you.
Australians wishing to follow an extended course of study are also required to apply for their entry visa from the nearest Italian Consulate PRIOR to their departurefrom Australia. Documentation from the school or institute in which they intendto enroll must be presented to the Consulate. The visa is renewable in Italy.
Onarrival in Italy approved students are required to register with the ForeignersBureau (Ufficio degli Stranieri) of the Questura, within eight days of theirarrival. This will enable the Ufficio degli Stranieri to issue the student withtheir "Permesso di Soggiorno". An entry visa issued in Australia withoutthe Permesso di Soggiorno is incomplete.
According to the following you would need to file a student permit. It says you can get the application at the local post office, trade union, or municipal office. I would call or go and ask.
Non-EU citizens in Italy for over 90 days require a "stay permit" (Permesso di Soggiorno). This is a permit to stay in the country and not a residence card; it is not obligatory for a foreigner to have residency in Italy provided they have a valid stay permit and are therefore registered in the commune.
There are a variety of permits, each specific to individual circumstances. It is important that the permit type correlates with the intentions of the permit holder; if the applicant has a visa, the two must correlate (student, not working, employed and so on). The Permesso di Soggiorno has a limited period of validity which matches the purpose for stay. Permits can be renewed.
The following are the most commonly-issued stay permits:
Application for the Permesso di Soggiorno can be made at the local post office, trade union or municipality office (until mid-2007 this was done at the local Police Headquarters, or Questura) in person, within eight days of arriving in Italy. The application can take up to three months to process.