Warriors started strongly and could have taken the lead inside two minutes when they broke down the right.
However, a strong Sale defence prevented Warriors capitalising on their first attack as they forced the ball out of play.
Fly-half Elliot Davies had two chances to give Warriors the lead but, on a windy day in Worcester, his early penalties both sailed wide.
After Sale had withstood a barrage of early Warriors pressure, they turned the tide midway through the first-half as they opened the scoring.
A Warriors pass was intercepted by Sale fly-half Tom Deakin on the half-way line and he ran unopposed to touch down underneath the posts before adding the extras.
The try seemed to kick Sale into life and only a determined defensive display from the hosts prevented the visitors stretching their lead.
The Warriors forward pack continued to work-hard, forcing a third penalty on the stroke of half-time. But with conditions deteriorating, Davies couldn't find the posts with his kick.
Hewitt's side came out after the break looking for an early score to get them back into the game, and they enjoyed an early spell of possession.
But it was Sale who drew first blood of the second-period after Deakin once again intercepted a Warriors pass before going over the whitewash.
The conversion increased Sale's lead to 14 points and, as defences dominated the latter stages, the two tries secured a win for the visitors.
After the match, Academy Manager Hewitt said: "I thought the boys played exceptionally well in the second-half playing into a very strong wind. We kept the ball for long periods but never really got field position to apply real pressure.
"We didn't take our opportunities in the first-half with the wind behind us. We missed a number of kicks at goal which Elliott would normally have kicked and our lineout did not function when we had Sale under pressure."
Warriors now face Northampton Saints this Saturday (9 February) in their penultimate game of the campaign. Kick-off on the A&H pitch at Sixways is at 2pm.
Warriors Under 18s
15 Jon Hughes
14 Jackson Hughes
13 James Young
12 Jack Wardle
11 Colin Dickson
10 Elliott Davies
9 George De Cothi
1 Joe Wrafter
2 Callum Young
3 Jack Cosgrove
4 Huw Taylor
5 Will Elt
6 Sam Smith
7 Andrew Boyce
8 Louis Chaudron
16 James Gunther
17 Dave Whiting
18 Lewis Hodnett
19 Matt Perks
20 Josh Feek
21 Luke white
22 Ted Parker
23 Ben Penfold