Hey,

Bachelor of Education (B.Ed.) is a 2 year post graduate degree in the field of Education.   B.Ed. in Mathematics can be opted by any student who has taken mathematics as a main subject in his or her graduation. This course can be done by B.Sc maths or B. A Maths students. Even B.Tech students can also go for B. Ed in Mathematics to teach Maths at higher secondary level.
There are certain eligibility parameters that one has to fulfill to study B. Ed in Mathematics. The students must have acquired a minimum of 55% aggregate marks in their graduation level.  They must also have passed one of the many entrance examinations conducted for B. Ed course.
Some colleges grant admission to B. Ed. courses on the basis of entrance test, so clearing the test becomes mandatory for those who wish to get admission in that particular college.
Students who wish to study B. Ed should clear any entrance tests conducted by various colleges and universities for admission. These exams are generally conducted in the month of June-July and carry Objective type questions. The results of entrance exams are released by July/Aug.
Top Institutes/Universities offering B.Ed. in Mathematics are:

University of Calicut, Calicut
Annamalai University, Cuddalore
Kapi College of Education, Madurai
CMS College of Education, Coimbatore
AWH College of Education, Calicut

Hope this helps.