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Good job getting a relatively white background. Exposure looks good on all of them except for 3, which is a little underexposed.
These could be tremendously improved with a little more understanding of different kinds of lighting. I'd suggest looking into resources for that. I would probably start off with "butterfly" style lighting as a good go-to for head shots. A few of them, especially the last, could benefit from a longer focal length. It looks like you might've been somewhere around 50mm? When you get that close to a face with anything less that 100-150mm, you start getting pretty noticeable distortion in the face - here we have a large forehead and bug eyes.
Crops are just a bit too tight for my liking. 2 has the best crop. I would shoot more for that. A little extra room will be appreciated as they can then print different sizes (particularly 8x10) without losing too much.
Hope that helps!