Manning, the nephew of Super Bowl winning quarterbacks Peyton and Eli Manning, threw for just 58 yards but rushed for three touchdowns.
Sterling Scott did most of the damage with 21 carries for 196 yards and another TD as Newman improved to 5-0.
The nation's top-rated sophomore quarterback came in having completed 61 of 81 passes for 928 yards and 11 scores, but he didn't need to pass. He completed just 7 of 12 attempts but the Greenies piled up 265 yards rushing with Scott leading the way.
Manning scored on runs of 1, 2 and 11 yards, the latter with 4:18 to go putting Newman up 31-20. But Riverside Academy came right back with a three-play, 65-yard touchdown drive capped with a 52-yard catch and run by
Andre Murphy. The two-point try failed, making it 31-26 with 3:24 to go.
The Greenies ran out the clock from there, with Scott rushing five times for 34 yards.
Riverside Academy (2-1) was led all night but the terrific all-around skills of quarterback-receiver-defensive back
Gage Larvadain, who completed a 38-yard touchdown pass to David Reynaud to go up 14-7 on the last play of the first quarter. On fourth down and 12 yards to go, Larvadain found Reynaud crossing over the middle. The speedy receiver made a beautiful catch and outraced the Newman secondary the final 25 yards for the score.
Just before halftime, Manning tied it up at 14-14 with his 2-yard score, before Scott finished the first possession of the second half with a 4-yard touchdown run, giving Newman its first lead, 21-14, one it wouldn't relinquish.
Laravadain, who came in averaging more than 300 total yards per game, had a 15-yard run on fourth down, a 45-yard completion, then ran it in from the 3, cutting the lead to 21-20 with 4:16 left in the third. But his two-point conversion try failed.
A Newman field goal gave the Greenies a cushion before Manning's 11-yard TD run seemed to put the game away.
Riverside Academy had other ideas, closing to within a touchdown on the long catch and run by by Murphy. But the Greenies were able to run out the clock, aided by a key third-down holding penalty on the home team. Manning was sacked on the play — he was sacked twice earlier — but the hold down field gave Newman first down at the Riverside Academy 40. Scott took over from there.
Manning finished with 13 rushes for 38 yards, including the sacks and two kneel downs. He now has eight rushing touchdowns on the year.
Newman, which had a huge game on both sides of the ball from sophomore tight end-defensive end
William Randle, continues its season next week at home against St Charles Catholic (LaPlace).
Many games in Louisiana this week were either postponed or canceled due to Hurricane Zeta.

Arch Manning threw only five passes in the first half of Friday's game at Riverside Academy.
File photo by Parker Waters