I think it's kinda funny that my group adopted what they saw as an "old school D&D" mentality when we first started playing 4E, and they went through 3 parties in 4 nights of gaming.
As I'm sure you will agree, old school means different things to different people depending on what edition they started playing with and how their game was run at that point. Attempting a definition is obviously beyond the scope of this thread, but I think it's safe to say that it's NOT supposed to mean that everyone dies constantly for no good reason. If this is happening in your game, I'm not sure it's old school.