I am always wanting to have my iPad displayed on the LCD screen, but plugging in the VGA cable is not ideal. First, you are locked into a single spot (and I am not a stationary teacher). Second, if you pick up the iPad and move it at all, generally the VGA adaptor pops out and you lose signal. All this is frustrating. That is why I invested in a great product: Reflector. I am by all means not trying to sell you on an app, but this is one that I can not live without. The Reflector App from AirSquirrels is a great tool to have. It is a little pricy ($12.99 for a single computer) but after I finally took the leap and bought it, I find the $13 not too much to have my iPad show up on the LCD without being shackled to a VGA cable.
If you have Apple TV, count yourself lucky. I work in a district that does not have Apple TV anywhere to use. I am always helping teach how to integrate iPads into the classroom and doing PD, small and large group, and need to show the iPad screen. As long as I have my Mac (the computer that Reflector is installed) plugged into the LCD cable, I can show the iPad form anywhere in the room. It is a thing of beauty It uses AirPlay to send the iPad screen to your compter that has Reflector App installed and then to the LCD! It is easy, quick, and works like a charm with no issues. I know there are other options out there, but I have really grown to love and appreciate this one! Check it out and give it a shot.