A yellow pentagon (five-sided) sign that points up means:

The pentagonal yellow sign with the point up is the school advance warning sign. It is shaped like a small schoolhouse and warns drivers approaching a school zone, school crossing, or school. The unique shape distinguishes it from standard diamond warning signs. School warning signs are placed far enough in advance of the school that drivers have time to slow and prepare for children, crossing guards, and school buses. School buses themselves require special yielding rules: when a stopped school bus extends its stop arm and flashes red lights, all traffic in most states must stop, often including traffic in the opposing direction on undivided roads.