Active Directory Rights

I have an asp.net application that will require users to in the Active Directory organizational unit 'Students' to authenticate and take a survey.  I followed the instructions from this article to link the authentication to AD http://msdn.microsoft.com/en-us/library/ms998360.aspx .  The problem is the credentials I use in the membership provider doesn't have the rights to read users information in the 'Students' OU and those accounts cannot authenticate.  The account I'm using has full control of the OU 'Techonosphere' and users from that OU can authenticate to the application just fine.  My question is what kind of priviledges does the account I use in my web.config need to authenticate users against AD?  Any information or resources are appreciated.
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