These two, at least, wouldn't have been trusted not to tell DD.

[Cathy Drolet]

No: HPFGUIDX 109150

RMM
"But what students?  All the students?  Or only those that Voldemort 
could trust not to tell Dumbledore.
Could he then trust the likes of Lucius Malfoy?  Crabbe?  Goyle?
Yes.
How about the Marauders?  Those rule breakers and daredevils?
Do you think that they wouldn't be attracted to the powerful magic 
wielded by this mysterious DADA teacher?"

DuffyPoo:
You've only just missed one thing. "And Snape was just this little oddball who was up to his eyes in the Dark Arts, and James -- whatever else he may have appeared to you, Harry -- always *hated* the Dark Arts."  If James hated the Dark Arts so much, why would he take a special class from a special teacher?  He wouldn't.  Sirius left his family, at 16, because he didn't agree with their pure-blood mania, being all for the purification of the wizarding race.  His parents were Dark wizards and Sirius wanted nothing to do with them.  He wouldn't have joined the special class either.  Lupin, a half-blood, wouldn't have been wanted in the class to begin with.  These three couldn't have been trusted not to tell DD what was going on. Would Pettigrew have joined if his idols didn't?  I doubt it.  It would have made another reason for them to shun him, and he wanted to get closer to them not be pushed away. 

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