All this happened, more or less.

Although the difference was slight, high-income children outperformed their less wealthy peers on both IQ tests and an exam designed to replicate achievement in various academic subjects. Lower income kids performed at a lower level than others in reading comprehension and mathematical calculations but were competitive in basic cognition, memory and reading skills, indicating that poverty may affect development at the level where different abilities must be combined, such as verbal skills and memory, in the case of reading comprehension. SciAm, May 18, 2007.