taught three languages

[azz]

a. He was a child taught three languages.
b. He was a child taught to speak three languages.

Are these sentences grammatically acceptable?
Are they natural?

 

[tedmc]

No.
I'd would say:
As a child, he was taught (to speak) three languages.

 

[5jj]

Are these sentences grammatically acceptable?
Are they natural?

Yes.
No. I'd say either what ted suggested or He was a child who had been taught (to speak) three languages..

 

[azz]

Thank you both so much.

Would they still be grammatical in the negative?

c. He was a child not taught proper table manners.
d. He was a child not taught to treat others with respect.

Would those be grammatical?

I suppose they are even less natural than my first two examples.

 

[tedmc]

Yes and yes. The negative versions actually sound better to me than the positive.

 

[emsr2d2]

I find the negative ones unnatural. A native speaker would say:

As a child, he wasn't taught proper table manners.
He wasn't taught proper table manners when he was a child.

As a child, he wasn't taught to treat others with respect.

 

[Annabel Lee]

a. He was a child taught three languages.
b. He was a child taught to speak three languages.

I think the reason for the unnaturalness has to do with the participial relative clause's being ambiguous in time reference there:

He was a child taught three languages (beforehand). [He had already been taught three languages.]
He was a child taught three languages (afterwards). [He would subsequently be taught three languages.]

 

[Tarheel]

Try:

While growing up, he learned three languages.

That's more likely to fit into a conversation.

 

[azz]

Thank you all so much.

Annabel Lee, I hadn't noticed that possibility at all! Thanks a million!
But couldn't the original two sentences also mean that he was a child being taught three languages?

I thought of this after reading your post.