Project Ready STEM Act - Amends the Elementary and Secondary Education Act of 1965 to authorize the Secretary of Education to award grants to national and regional intermediaries and, through them, subgrants to their community-based affiliates to operate in-school, after school, summer, and weekend programs that focus on science, technology, engineering, and math (STEM) education.

Defines a "national intermediary" as a national private nonprofit organization that has: (1) a network comprising community-based affiliates in at least 50 urban communities, (2) expertise in overseeing programs to help middle and secondary school students succeed, and (3) operated in at least 25 states continuously for at least 20 years.

Defines a "regional intermediary" as a private nonprofit community-based organization that has: (1) a network comprising community-based affiliates in a prescribed region, and (2) expertise in extending educational services to middle and secondary school students.

Requires the STEM programs to primarily serve students who are traditionally underrepresented in STEM field careers, and include project-based learning opportunities and individualized instruction.

Directs each subgrantee to collaborate with an institution of higher education in providing such services.

Requires grantees to direct at least: (1) 50% of their grant to community-based affiliates that are successfully operating STEM programs so that they can expand them to reach more students traditionally underrepresented in STEM field careers, and (2) 25% of their grant to the development of STEM programs by community-based affiliates not currently operating any.