Divide the class into teams of around 4 or 5 to end up with even groups.
Groups must think of a five letter word. They compete against another team.

They must guess the word by writing a five letter word down.
The opposition tells them how many letters are correct in the word, but not which letters.
Example: Your word is "clash" they guess "beach" there are 3 letters that are similar (c,a,h).

Next they may guess "PedagoNet" which contains no correct letters.

They continues untill they identify the correct word.
Each team takes a turn. The first team to guess the word wins.
Hint : Keep a note on impossible letters and probable letters.

A game can last a while!