Final answer:
Ms. Sanford likely identifies structural issues within economic and housing systems as the key systemic problem exacerbating poverty, as unstable housing is highlighted as a significant cause of poverty.
Step-by-step explanation:
The key systemic problem that Ms. Sanford likely claims, as inferred from the provided reference material, is the structural issues within economic and housing systems that exacerbate and perpetuate poverty. While discussing the high costs of rent and the exploitation by landlords, the material suggests that unstable housing is a significant cause and not just a condition of poverty. Additionally, the discussion about increased financial resources failing to yield measurable gains in student performance prompts education experts to consider structural problems rather than solely resource-based issues as a root cause for systemic challenges.