04/30/2013 02:30 pm ET

Walton Foundation Gives $8 Million To StudentsFirst -

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A foundation associated with the Wal-Mart family fortune has expanded its support for the education advocacy group run by former District of Columbia schools chancellor Michelle Rhee.

The Walton Family Foundation announced Tuesday an $8-million grant over two years to StudentsFirst, which is headquartered in Sacramento but has operations in 18 states.

Rhee established StudentsFirst as a political counterweight to teachers unions and has pushed, mostly at the state level, for policies that include limiting teacher tenure, easing rules for dismissing teachers and making student test scores the major factor in an instructor's evaluation.