You talk about choosing a major. I take it then that you're not in the UK? Well anyway:
Most people here go either through a four year education BA with QTS incorporated, or a three year subject BA followed by a one year PGCE. Even if you teach SEN, you have to have a subject specialism related closely to the curriculum of the age group you intend to teach (eg. maths, english, art, PE etc). However, it's not unusual for teachers in SEN to have psychology in their degree profile.
You need no special qualifications here to teach SEN, other than a first degree and QTS, but many teachers in the field go on to take masters degrees in SEN.
What's more important is enthusiasm for helping others to get the benefit of a subject you love, no matter what their intellectual capacity.