Three pert stories about willful Sara--and wise old school custodian Mr. Zamatsky, who twice gets her off the hook (and prompts a magnanimous act the third time 'round). In story #1, Sara ditches her unwanted boots on the school bus and then, when the first snow comes, can't go outside with the other children to play; but Mr. Zamatsky, inquiring into her plight, lends her his--stuffing them with paper and tying them with string as his mother did when ""we had only one pair of boots for me and my seven brothers and sisters."" (And, exclaim the children, ""She can make the biggest tracks of all!"") Story #2 finds cranky Sara pinching everyone and exiled from class--whereupon Mr. Zamatsky produces some clay, pinches it into a face, and eases her reinstatement, clay in hand; ""Mr. Zamatsky says I am a very good pincher!"" In story #3, ""Sara's Birthday,"" she's at her assertive worst--insisting that, as the birthday girl, she should have her druthers in everything (""I'm glad you have a birthday only once a year,"" says much-affronted Sam). But the cupcakes that Sara's mother brings for the class present a knotty problem: Sara Wants to give one to Mr. Zamatsky, her mother won't let her deny one to censorious Sam, teacher Miss Sherman says she does indeed like cupcakes--and Sara finally concludes that, as she's had so many other perks, she can give up her cupcake to Mr. Z. Or, ""I don't need a cupcake because l,m the birthday girl!"" (He knew it all along, Mr. Z. tells her, on account of the blue ribbon in her hair.) Not great (too situation-bound for that), but nicely done.