I'm sure you're right, there probably is less emphasis on the 3Rs. I still think the biggest problem in lower income schools in parental apathy.
Several years ago I worked for a company that did some pro-bono work for the city's public school system. Our company specialized in employee motivation and sales incentive programs. Want to know the #1 objective the school district wanted us to achieve? Higher attendance. Absenteeism was out of control, much higher than the suburban school districts. Poor attendance is just one example of parental apathy.