by Chelsey Cooley Sat Sep 19, 2015 8:36 pm
The issue with your example actually doesn't have much to do with "as", etc. It's wrong because of a logical error in the comparison.
"Studies of test scores show that watching television has a markedly positive effect on children whose parents speak English as a second language, as compared to those whose native language is English."
In this incorrect sentence, we're trying to compare two groups of children: children whose parents speak English as a second language, and children whose parents speak English natively. But as written, the second half of the comparison is logically wrong: if "those" refers to children, then it doesn't make much sense to compare children whose parents are ESL with children who are native speakers (there might, for instance, be some overlap between those groups). If "those" refers to parents, then we're comparing children to parents, which also doesn't make sense.
The correct version successfully compares one group of children to another distinct group of children.
My understanding is that "compared with" and "compared to" are more or less equivalent on the GMAT, and "as compared" is one of those things that's probably wrong but that you shouldn't base an entire answer on.