Personally, I use “but” and “so” to start sentences, but not “and” and “because”.
Today I was talking to a friend of my brother on this matter, who is in 6th Grade. He takes tuition from a private tutor who told him that in early days using “and”, “but”, “so” to start a sentence was okay, but now-a-days it is becoming obsolete and that we should not use them to start a sentence. He is a reputed teacher here and he keeps track of current affairs. (He is the one who told me, when I was his student, that “will” is being used after “I” now-a-days and I followed the advice.) So I could not deny this information. Tried to find in Google about this but no source made me think it is trustworthy. So I would like to know this in StackExchange,
What is the actual rule and is this rule being changed?
PS- I don't use “because” to start sentences but I always had a doubt. So I added it!