Query: what is a key aspect of the gates foundation in the US
Context: A key aspect of the Gates Foundation's U.S. efforts involves an overhaul of the country's education policies at both the K-12 and college levels, including support for teacher evaluations and charter schools and opposition to seniority-based layoffs and other aspects of the education system that are typically backed by teachers' unions. It spent $373 million on education in 2009.