No one would deny that some of us have had advantages over others. But it's a long way from saying that "environment matters" to saying what about your environment matters.
In both politics and charity, we hear many proposed "solutions" for poverty and inequality. Most of these solutions have been tried. Very few have been tested. And of those that have been tested, many just don't work.
Education. The New York City Voucher Experiment offered scholarships to low-income students, so they could attend the school of their choice. The effects were small to nonexistent, as we discuss here.
Childcare and job training. The Comprehensive Child Development Program brought case managers to the homes of low-income families to offer them direct counseling and refer them to local services (job training, childcare, etc.) The program had little or no effect on families' economic conditions or children's cognitive and social development, as we discuss here.
Scared Straight (now known as Juvenile Awareness Program). This program takes juveniles on tours of prisons to deter them from committing crimes. Repeated randomized controlled trials have not shown that the program reduces criminal behavior, and a high-quality review of nine separate trials of the program by the Cochrane Library concludes that the program is actually "likely to have a harmful effect and increase delinquency relative to doing nothing at all to the same youths." Nevertheless, as of 2011, it continues to be funded (archived here). (The review co-authored by the Cochrane Library and the Campbell Collaboration is available in this PDF file).
More examples. In a guest post on the GiveWell Blog, David Anderson of the Coalition for Evidence-Based Policy estimates that 75% of rigorous evaluations show weak effects, no effects, or negative effects, and gives several more examples including educational software and family literacy programs.
There are also success stories, such as the Nurse-Family Partnership. A larger list of well-studied programs is available via the Coalition for Evidence-Based Policy, though these programs are not necessarily connected to particular charities.
The programs listed above are among the few social programs that have been given serious, careful study. Most charities' programs have simply never been seriously evaluated at all.