The minimum criteria to pursue B.Sc/BA  Psychology is that you should have studied 10+2 or an equivalent course from a recognised University. Now you might wonder if you can study Mathematics and pursue Psychology. Some Institutions expect a minimum aggregate of 50% in your 10+2 or equivalent exam in Science Stream.  Some Institutions take admissions based on Entrance Examinations while some Institutions take admissions based on Merit in your qualifying examination. You also can opt for Distance Education. So you should select those Institutions which allow you to pursue Graduation in Psychology with Mathematics as a subject. There are Institutions which accept Mathematics. So it cannot be ruled out. You can study Mathematics and then pursue Psychology in Graduation.