No. You cannot take a B.Ed. immediately after completing 12th grade. B.Ed. is professional courses for those who want to become teachers. A bachelor's degree, such as B.A., B.Sc., or B.Com., is prerequisite and primarily, candidates take up B.Ed. after completion of their undergraduate education with overall marks of 50-55% (depending upon the institute). Some universities also conduct entrance exams for admission.
B.Ed. degree is for two years, wherein different teaching methodologies, educational psychology, and classroom management techniques are covered. But if you want to join the teaching profession directly after 12th, then you can take four-year Integrated B.Ed. program such as B.A. B.Ed. or B.Sc. B.Ed. wherein graduation education with teacher training together takes place. These courses can be pursued under institutions such as NCERT-affiliated Regional Institutes of Education (RIEs) and under some state university.
Or alternatively, you might opt for Diploma in Elementary Education (D.El.Ed.) or the Primary Teacher Training (PTT), which would serve as eligibility credentials for primary teacher positions. But the decision upon which one to choose varies with the selection of your objectives and the cadre of teaching for which you want entry.