The original sentence should not have a comma. It might help if it were written as follows: "It is noticeable that for both types of household with children a higher-than-average proportion were living in poverty at this time".

I agree with Randy that writing the sentence with just a single comma makes it a little harder to parse grammatically. The sentence could be written with two commas - "It is noticeable that, for both types of household with children, a higher than average proportion were living in poverty at this time .’ When you have a phrase separated from the rest of the sentence by commas, the sentence should make sense with the phrase removed. Thus - "It is noticeable that a higher than average proportion were living in poverty at this time." What the sentence is saying is that, for some subpopulations of the overall study population, "a higher than average proportion were living in poverty at this time". Which subpopulations? "both types of household with children". I can't explain further without more of the original context.