Student visas allows to limited in time working activities (part-time occupations). Time limit is 1.040 working hours a year, freely spread through out the year, its months, its weeks and its single days. The fact that student visas allow to work for a limited amount of hours, local labour departments believe that the turning to self-employed visas is not possible. Law provides for that the conversion to subordinated work, both open-end contracts and determined ones, is possible, this allows to being able to renew papers in Italy.
In other words, in theory a student, without leaving Italy, could turn his/her visa into a work one, only if flow decree quota are available.
Usual procedure: conversion application form can be taken to police headquarters after employers gave in to local Labour Departments the application asking for the authorization to subordinate work.