Kents Hill School (also known as Kents Hill or KHS) is a co-educational independent college-preparatory school for boarding and day students.
 Kents Hill is located in Kents Hill, Maine, 12 miles west of the state capital of Augusta.
 It is the 30th oldest boarding school in the United States and one of the oldest continuously operating co-educational college preparatory schools.
 One of the three oldest Methodist academies in the United States (with Cazenovia and Wilbraham), the school is now a member of the Association of Independent Schools in New England (AISNE) and accredited by the New England Association of Schools and Colleges (NEASC).
Head-Royce School (Head-Royce or HRS) is a co-educational college-preparatory K-12 school in Oakland, California.
 The forerunner of Head-Royce was the Anna Head School for Girls in Berkeley, founded in 1887.
 Relocated to its current site in 1964, Anna Head School for Girls merged with the neighboring Royce School in 1979 to form the present-day Head-Royce School.
The Inter American University of Puerto Rico ("Spanish": Universidad Interamericana de Puerto Rico; abbreviated UIPR) in Spanish, and often referred as ""Inter""— is an ecumenical Christian university in San Germán, Puerto Rico.
 The UIPR is a private co-educational university system in Puerto Rico.
 It was founded in 1912 in San Germán, Puerto Rico.
 The University has campuses in Aguadilla, Arecibo, Barranquitas, Bayamón, Fajardo, Guayama, Ponce, San Juan, and San Germán.
 The school also has three professional schools: School of Optometry, School of Law, and the School of Aeronautics.
 The Inter offers academic programs in 11 teaching units.
 The San Germán campus is also the home to the Inter American School, a private co-educational college-preparatory school.
Woodward Academy (also known as Woodward or WA) is an independent, co-educational college-preparatory school for pre-kindergarten to 12th grade on two campuses located in College Park, Johns Creek, Georgia, United States, within the Atlanta metropolitan area.
The Branson School (also known as Branson, Branson School, or KBS) is a co-educational college-preparatory high school for students in grades 9–12.
 The school has 320 students, and is located in Ross, California, 11 miles north of San Francisco.
Darrow School is an independent, co-educational college-preparatory school for boarding and day students in grades 9-12.
 Its New Lebanon campus is a 365 acre property just to the west of the boundary between New York and Massachusetts in the Taconic Mountains and within the Berkshire cultural region.
Holy Trinity Catholic High School or HTCHS is a private high school in Temple, Texas.
 Holy Trinity Catholic High School is a private, co-educational college-preparatory school.
 It is located in the Roman Catholic Diocese of Austin.
Mary Richardson Walker (April 1, 1811 – December 5, 1897) was an American missionary.
 She was the daughter of Joseph and Charlotte Richardson of West Baldwin, Maine.
 Both parents were school teachers and valued education for all their children.
 She attended Maine Wesleyan Seminary.
 Mary wanted to be a missionary and applied at the American Board of Missionaries, but she was turned down, because she was not married.
The Tshimakain Mission started on August 29, 1838, with the arrival of Presbyterian missionaries Cushing and Myra Fairbanks Eells and Elkanah and Mary Richardson Walker to the area along Chamokane Creek at the community of Ford, Washington.
 Fort Colvile Chief Factor Archibald McDonald recommended the area to Eells and Walker on their first visit to the area.
 On April 23, 1838 after traveling to Independence, Missouri, the Eells, Walkers, William Henry and Mary Augusta Gray, Asa B. and Sarah Smith, and Andrew Rodgers, departed for the Oregon County with a Hudson Bay Company fur trader caravan to the Rendezvous.
 They arrived at Waiilatpu and the Whitman Mission on August 29, 1838.
Trinity-Byrnes Collegiate School (TBCS) is a co-educational college-preparatory middle and high school located between Darlington, South Carolina and Florence, South Carolina.
 The school is on a 100 acre campus southwest of Florence and serves students in the Pee Dee region of northeast South Carolina.

Question: What co-educational college-preparatory school is located in the same state that Mary Richardson Walker's parents were from?
Answer: Kents Hill School