The latest in the long line of Maverick Teacher Inspires a Group of Bright but Undisciplined Students to Pull Finger and Be The Best They Can Be films, The History Boys distinguishes itself by being based on a play, set in the eighties, and very little else.
The 
first half of the movie is actually pretty good, the characters are believable, the script is genuinely witty and the premise, although hackneyed, is well introduced. Unfortunately, without spoiling the plot, the film slowly veers away from reality towards the end as it trundles towards the regulation bittersweet ending. I think the producers tried to avoid the trap of being too preachy by revealing that just about all the characters in the film are unlikable to varying degrees.
Not really recommended.