Here's the rule:

From the National Federation of State High School Associations 2001-2002 Wrestling Rules Book

Rule 4, Section 3, Article 1

Special eqipment is defined as any equipment worn that is not required by rule. Any equipment which does not permit normal movement of the joints and which prevents one's opponent from applying normal holds shall not be permitted. Any equipment which is hard and/or abrasive must be covered and padded. Special equipment includes, but is not limited to, hair coverings, FACE MASKS, braces, and support.

As an official and life-long wrestler, I have never seen a wrestler who wears a mask use it to his advantage. If you have seen one that has, then that match was poorly officiated. A good official just would not permit something like that. I agree with coach. If anything, a mask-wearing wrestler is at a DISadvantage, due to limited visibility. A good cross-face will turn anyone's head, even if they're wearing a racing helmet.

Good luck!