Every time you teach something it reinforces your understanding of what you are teaching.

That is an interesting question. I do not know if there is 'equal gain' since it depends I think on the way the mentor is 'open' to a student teacher. And even the other way around some student teachers do not learn so much from their mentors.

However, based on experience with mentor teachers I have often heared them report learning from their student teachers because they challenge them to explain why they behave the way they do in the classroom. Also, they often indicate to learn from seeing student teachers teach their classes, sometimes in innovative ways.

I think it is a mutual learning process.

Thanks colleagues for your inputs. I believe that the teachers who accept student teachers into their classrooms are very fortunate. While I would like to believe that there are many student teachers who can teach their mentors in schools I am very aware that in reality that is unlikely - except where the teacher is willing to learn new things and the student teacher is very strong and confident. From my experience with my student teachers this does happen sometimes but it is relatively rare.

When you mentor others, you end up discovering a lot about yourself. You grow as a person, a human being. The most unintended outcomes of mentoring others are the qualities you discover/develop in/of yourself. In addition, you develop a network of people you can link to/with. So, mentoring is a two-way street; you learn so much from/about your mentees as your mentees learn so much from/about you. As they grow, so you grow. You may even end up life-long friends and colleagues. It is a good thing to mentor others; not just mentoring but a form of frientoring is better. But, keep it professional and friendly; both formal and informal, teaching and learning together. I ran a program where I mentor university students to mentor high school students and the mutual benefits have been so astounding and rewarding all along. Some of the grade 9 learners we started with are now 1st year students in my university. They made sure they sought me out to let me know that they made it into the university; two years after the program ended due to funding. Some of the student-teachers involved learned to teach differently and even went back to the schools where we mentored to teach; they are now teachers teaching in places they didn't initially consider they could teach in and some who where non-teaching majors at the time have changed majors to become teachers. Some others started mentoring in the school where they became emplyed as teachers. Some re/awakening took place.

In this case it is a close relationship that will benefit all. They have won the teachers and students. The most theoretically will benefit students. Teachers form their new skills, will have access to new informations.

Students will be the most capable for  new skills.

Think the mentor will learn something from the student's teacher but not sure will be the same amount (if can quantifiable).  Because this is analogous to a part-time lecturer that can learn from his o her working adult students during the night classes.  It is normal that something a mentor shared with the teacher & after the teacher had processed it & s/he might has his or her own feedback to the mentor.  This is because different person has different background, experience & mental models that can offer something unique as feedback.