The Twins' Mystery Teacher (Sweet Valley Kids, No. 3)

Who's Mr. Marshall?

Elizabeth and  Jessica Wakefield are identical twins who sit side by  side in their second-grade class. When their teacher  is out with the flu, everyone changes seats, and  the substitute teacher can't figure out who anyone  is -- especially Jessica and Elizabeth!

  That's when the new substitute teacher arrives. Mr.  Marshall is very strict, and the class is on its  best behavior. Then the twins see Mr. Marshall  getting into a police car. Could he be a dangerous  criminal? When the class finds out who he really is,  they are in for a big surprise!