just as the sun sliced over the mountains east of San Diego, Guadalupe Dukes and her 6-year-old grandson, Gael, sat in their car, waiting for the school bus to arrive on California Highway 94.

Zoom in: San Diego Unified currently has 13 electric buses in its fleet of more than 400. The district will also soon replace 30 diesel buses under a grant through the EPA's Clean School Bus Program .

SAN DIEGO (FOX 5/KUSI ... The Association of International Educators estimate in the last academic school year international students contributed $43.8 billion to the U.S. economy.