Do schools use grants first or loans?

If you make so much money in grants can you go and blow that on a bunch of random classes you need? or are they going to use grants and loans at the same time? Even if your grants cover everything? Like lets say you need food handler card, restaurant management, customer service classes and you can get each one individually for cheap. So you are more qualified to work can you do that? I was just told they will take out loans at the same time as your grants even if the grants cover it. Which I dont understand since they are paid either way right?