Care would need to be taken to keep the distance between the pupil
(his whole head actually) and the camera, also his position within the
frame and a fixed zoom setting on the camera so that the Photoshop
Action would give consistent results.

Tripod and bench.

Spend 2 hrs getting the process set up right and then 10 seconds on
each kid. Make 'em hold a white board with their name on it (or
student number etc) that stays in-shot but doesn't obscure their face
but will be cropped away. That way you can identify the kid before
cropping so that once the crop action is done you can save the file
based on the kid's name. It also helps if the kids are photo'd in
surname order within their class.

--
Owamanga!
http://www.pbase.com/owamanga

Use Photoshop > file Menu > Automate >  Contact Sheet. Then choose how may
per sheet of whatever paper size you use.

The U.S. State Department has a guide for passport photos at
http://travel.state.gov/pdf/Photo%20Guide%2010-01-04.pdf.  In practice, they weren't
stringent when my wife and I renewed our passports last year.  We photographed each other
against a white wall, with indirect lighting from a halogen lamp in the room.  I cropped
the photos, sized them to 2X2, and printed them on my inkjet printer on normal photo
paper.  They were accepted, although when the new passports came I realized thta my
picture was somewhat dark.  And I'vce used the passport several times, to enter several
countries and to return to the U.S., without any problems.  I used the same photos when I
needed visas for Viet Nam and Cambodia.