During my career, my company recruited intern for all disciplines, from Engineering field to Administration. Duration from as short as 10 weeks to 9 months and its varies from university to university. I have memorable experience leading Internship Program for a period of 18 months.
For a student, they experience 9am to 5pm working life, office politic and expose to what the market really needed.
As a company, it is a minimum cost to hire and demostrate the mentor leadership and a talent pool for future placement.
Is all internship program successful? Not really, some mentor assign a good project and intern gain knowledge from it, some mentor just want a spare hand, trigger a red flag.
So, when you are think of runing a internship program, you need to make sure you have a project and a mentor to coach them.