What kind of classroom is it? Kindergarden? Middle School? High School? What kind of class it is suppose to be? Art class? Biology class? History class? I ask because when it comes to those kinds of questions, the classroom type is not the same. When I was in Kindergarden, we didn't have tables in the classroom. In first grade, we had long tables we worked at. In middle school through high school, we had some desks (and it depended primarily on the subject). For science classrooms, we had work stations that required us to sit on stools to work at. For art class, we had tables, and two areas separated from each other (one for pottery, the other for painting). For my English classes, they often had bookshelves that had books on them.
One you've figured out that answer, then start looking at Craigslist or Freecycle to see if you can get your hands on furniture and required stuff. Also, you may want to consider making the design unique. My English and Psychology class (which were both taught in the same classroom by the same teacher), had not just desks, but had an old wingback chair that the teacher allowed students to sit in during class time (I know that before I even had him, he once had a couch in addition to the chair in the classroom that he allowed students to sit on).
So, it depends on what school, what type of class and what you want to convey as a teacher's class room.
