OK, since we've been mostly talking about 'Evil Strawberries', here's a little testament about my game.
(BTW: I tweaked it so that the kids have one city, it started in 2006 and all units were free for the kids [The teachers still gotta get paid.]

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After I smashed that Line O' teachers I took the 6th Grade Science and 6th Grade History relatively easy. Then I laid seige to 6th Grade Math and 6th Grade English. When I gained them I placed a Stack O' Doom of 'Kids with a Stick' in the halls to defend against invading teachers.
I built up my military a little more and then I was off!
Very slowly I took the gym (6, count 'em 6 different cities there!) Then I conquered the Boy's Locker Room, and the Storage Room. When I went for the Girl's Locker Room I lost about 2/3 of my 'Kids with s Board'. (I guess the girls don't like use peekin' in

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I rebuilt my military, very, very slowly because I was ambushed by a kindergarten raiding party, then I finally took the Locker Room. From that point on I slowly gained every room in the "school" except the main office. As I was busy attacking the office a teacher strike-force slipped unnoticed to my first captured city,
and my biggest, 6th Grade Science!
It fell to their forces
Finally I broke the
Seige of the Office and raced back up to 6th Grade Science where I met a Teacher Army!! We engaged. I sent three 'Kids with a Board' up North and retook the city, er classroom.
It took about One and a Half Hours to defeat the Evil Alliance of all Teachers and Student Teachers! (also known as E.A.T.S.T --pronounced Eats Tea--)
Hey! Maybe you should add 'Student-Teachers' they can be drafted!