Keynote in the classroom
 

I use keynote along with my MacBook Air 2012 in my instruction for Science and History. The projector I use is not HD and I connect using a thunderbolt to VGA converter. When I connect, the projector display is ok but the screen on my Mac is very large. I have to disconnect the projector in order to close out a screen. Is there way for the projector screen and my Mac screen to be of similar size proportionately? I get tired of always disconnecting the projector anytime I need to make changes to my keynote project.

When you say the screen on your Mac is very large I assume you're referring to resolution? The question then, is what resolution are you using on your Mac? (Tell us which Mac you have.) Your Mac should always be set at its native resolution. The VGA resolution of the projector is probably set at something like 800 x 640 or maybe lower depending on the type of projector you're using. You can't change that.

I have a Macbook Air 13-inch, Mid 2012
1.8 GHz Intel Core i5
4 GB RAM
Running Mavericks 10.9.2
My screen resolution is set at Scaled 1440 x 900

The native resolution is correct for your model MBA (1440 x 900). The problem is that you have it set to scaled which will make objects appear larger - especially print. Uncheck the option for scaled and see if that helps.

Thanks, I'll have to wait until Monday to try this but I thank you for your quick reply.