How to correct this sentence?

[MPoppins]

Hello! I was asked to correct a class test and the following sentence was marked as grammatically incorrect:

"The houses were more bad than good."

Specifically, "more bad" is marked as incorrect. Now, it doesn't sound brilliant to my ears, but by now I seem to be completely stumped, as embarrassing as it is. Below are some of my thoughts:

"The houses were worse than good"

Eh... doesn't sound quite like it...?

"The houses were rather bad than good"

Does that make sense....?

"There were more bad houses than good houses"

Is that the meaning of the original sentence?

I hope someone can tell me what I'm missing. What exactly is the grammar error? And how can I correct the sentence?

Thank you.

[Alan]

There is nothing grammatically wrong with the sentence.

From a stylistic viewpoint, however, e.g.

The houses were bad rather than good.

would be slightly preferable.