Furniture:
* Tisch - table
* Stuhl - chair
* Schreibtisch - desk
* Tafel - blackboard (can also be whiteboard - Whiteboard)
* Regal - shelf
* Schrank - cupboard
* Fenster - window
* Tür - door
* Wand - wall
* Lampen - lamps
School Supplies:
* Bleistift - pencil
* Radiergummi - eraser
* Stifte - pens
* Lineal - ruler
* Schere - scissors
* Buch - book
* Heft - notebook
* Mappe - folder
* Block - pad
* Papier - paper
* Schreibblock - notepad
* Taschenrechner - calculator
* Globus - globe
* Karte - map
* Bilder - pictures
* Poster - posters
Other:
* Lehrbuch - textbook
* Arbeitsblatt - worksheet
* Markierungsstift - highlighter
* Kreide - chalk
* Schwamm - sponge
* Mülltonne - trash can
* Wanduhr - wall clock
* Computer - computer
* Beamer - projector
* Internet - internet
* Kaffee - coffee (for the teacher!)
Bonus:
* Lehrer - teacher
* Schüler - student
* Klasse - class
This list is not exhaustive, but it provides a good starting point for understanding classroom items in German.