55 years, yet the lower test scores persist. I think early childhood education plays an important part, but I don't know what other problems explain the low test scores.
Head Start, Vista, mentoring, free school lunch and breakfast programs, etc. have seemed to yield disappointing results. Tons of things have been tried for decades by the government and all sorts of organizations. Senator Daniel Patrick Moynihan was insightful with his injunction against "the soft bigotry of low expectations."