ตำแหน่งใดมีโรงเรียนมัธยมปลายกรีนวัลเล่ย์?ไม่จำเป็นต้องใช้โต๊ะทั้งหมด
Which position has a School of green valley high school?It is not neccessary to use all the tables.
 table_57550:  "Player" [ text]  "Position" [ text]  "School" [ text]  "Hometown" [ text] 
SELECT "Position" FROM table_57550 WHERE "School" = 'green valley high school'