Peer tutoring is one way of building a new student's confidence. Not only do they receive tutoring, they also receive instant encouragement that they, too, can excel and find themselves in the same place their tutor is at now.
But there are some major benefits to peer tutoring for the tutors also. It's been said that the best way to learn is to teach and, so long as the peer tutor is ready for the job, that's certainly true.
Peer tutors receive a natural confidence boost from teaching and interacting with other students. They get to look back at the mirror of a younger, less experienced student and see where they themselves came from not so long ago. This, in turn, lets them measure and appreciate how far they've come since.
Make no mistake about it, peer tutoring is a serious challenge--this makes it the perfect assignment for overly-gifted, overly-bored students you just don't know what to do with. Suddenly your student will be forced to explain not just what happens within the Spanish language--or other languages, too--but why. You can rest assured that the student is going to bring up angles and questions about the language that the peer tutor may not have considered before. This is part of the challenge. Inevitably your peer tutor is going to come up against a question he doesn't know the answer to. What he does then is part of his own learning process: He has to step back and analyze the information he's already been given, possibly even search out new information, in an attempt to find out what the answer is.
It's imperative that a peer tutor knows he can come to you for help and answers if he's stumped. Think of peer tutoring not as fully independent teaching but an added responsibility that should be well-rewarded within the framework of your grading system. The peer tutor is taking a first step out on his own, but still under your guidance. As you monitor his progress you'll have a chance to mentor him not just in Spanish but also in teaching technique. He'll develop a clearer understanding of his own language skills, the confidence of being able to communicate that information to another and the pride of making full use of his burgeoning language skills. His language abilities will develop all the faster because he's using them to the fullest--his vocabulary will expand as the student receiving tutoring challenges him, as will his grasp of grammar as he's forced to examine it from new angles.