If your course took more then 90 days then You have to apply the Permesso di siggorno (Residence Permit). A Permesso di siggorno issue from 6 months to 1 year depending on your course length.
A student visa would be only for the entry and after enter in italy you have to apply for the Permesso di siggorno (Residence Permit) in the local Questura (Immigration Department).
It will normally cost 250 euro for one year that contain one year medical emergency insurance.
If you apply for 6 months permesso di siggorno then it will cost you around 180 Euro.