Turner, a 6-foot-8 forward out of Chicago (Ill.) Lab School, gave Northwestern a verbal pledge on Sunday.
"It just seemed to be the perfect fit for me," Turner told Scout.com. "It was everything I was looking for both academically and basketball wise."
Turner, who is known for his skill and athleticism, also considered Pennsylvania, Harvard and Valparaiso.
"Just the mix that they have said," Turner said when asked why he picked Northwestern. "Besides maybe Stanford, nobody has the prestigious that Northwestern has academically and basketball wise. Plus it's in the Big Ten."