Hamilton went 5 of 9 from 3-point range and 7 of 11 overall and made all six of his free throws. Blackston was 10 of 11 from the field. Iwin Ellis and J.D. Wallace had 10 points apiece for the Panthers (3-11) and Dennis Jones had eight points and 10 assists.
Prairie View A&M shot 70 percent (21 of 30) in the first half with eight 3-pointers. Hamilton had 22 points and Blackston 18 as the Panthers opened a 59-32 lead over the Bulldogs, who shot 52 percent.
The lead reached 40 less than five minutes into the second half. All 11 players scored for the Panthers.
Isaiah Lopez had 12 points for Jarvis Christian.
Mannion, who recently reclassified and is ESPN's No.11 overall player in the class of 2019, chose Arizona over Marquette.
He'll fit in with Sean Miller's plans for a faster tempo on offense.
The cream of the crop of American high school basketball will congregate in Colorado Springs from Oct. 5-7, as USA Basketball unveils its newly expanded Junior National Team minicamp in collaboration with the NBA, NCAA and NBPA.