Hi b - in the future, please put your question fully in the body of the message, and don't rely on the title. If you're using a mobile device, it can be tricky to see both.
It's grammatical, but hard to parse in your head and there are simpler ways to express yourself.
My teachers have really helped me.
I've been helped by many teachers.
I think that the sentences you suggested have a little different meaning. The writer hasn't been directly helped by the teachers, it was just the fact they taught him.
So you're saying that they are not actually good teachers, and didn't actually help him, but they are so well known that simply saying "X was my teacher" gets that person an advantage? If that's the case, fine, but 99.5% of people who come here to learn English would mean the more simple situation I describe.
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