IT isn't very demanding. All your laptop really is in IT is a dumb interface for some type of Remote Desktop program and other diagnostic tools that are mostly just limited by the interface speed to your network. How quickly you can work with a Server is more a limit of how responsive the server is, network connection and speed you are capable of thinking and working input devices not your laptop.
Since this is for college courses your computing demands are even less. I'd be more concerned about weight and battery life as you'll be carrying it around all day. If you want it to feel fast an SSD on a i3 will feel much faster in most situations than an HD on an i5.
All that being said with a $600 budget I'd strongly consider the HP Pavilion 13-s128nr x360. It is pretty lightweight at 3.77lbs. It is a 2in1 so it can double as a tablet. The battery life is up to 11 hrs 45 min. It has a nice and sharp 1920x1080 screen. It also has an i5-6200u CPU, 8GB RAM and a 128GB SSD. The real downside is it is pretty thick.
http://www.amazon.com/...014X4UAUI/
This Dell Inspiron i7359-4371SLV is quite a bit thinner. It uses a 500GB HD + 8GB SSD hybrid drive instead. All the other specs seem the same as the HP. I'd get this if you want something thinner to carry around. Although I'd dump the hybrid drive as soon as you can afford it in favor of a large SSD. Given that it likely has an M.2 port for it's current SSD. You might be able to install an ultra fast Samsung SM951 if you saved up. Although I have no way of knowing if it will fit.
http://www.amazon.com/...00TUQ6HM0/
Really my key points why I selected those laptops is lightweight, good battery life and at least 1920x1080 screen. Being as they are being used for college and IT. You should get practice on proper security and setup hard disk encryption on them. Also get in the habit of using a password manager like Lastpass.