Six months into the school year, Mrs. Baker gets a telegram--and telegrams are not usually a good thing in this novel. The Wednesday Wars by Gary Schmidt is set in the 1960s, during the Vietnam War, and many women were recieving news of their loved ones in the military via telegram. As you can imagine, the women who received telegrams were generally receiving bad news in some form; in this environment, no news would have been good news and telegrams were generally bad news.
Mrs. Baker's husband left for the war at the beginning of the school year, and one Friday afternoon Mr. Guareschi, the principal, comes into her room and gives her a yellow telegram. After reading it, Mrs. Baker runs out of the room. Holling Hoodhood picks up the telegram she dropped, and this is essentially what it said:
DOWNED HELICOPTER TRANSPORT STOP KHENSAHN STOP LT T BAKER MISSING IN ACTION STOP
What the telegram means, of course, is that Mrs. Baker's soldier husband is now missing in action, and neither she nor the military knows where he is--or of he is even alive. This is devastating news, of course, but Mrs. Baker is back in class on Monday and does not let her personal tragedy interfere with her classroom duties.