Brighton and Hove need 23 points from their final home game with Eastbourne on Saturday to take the title from Hastings.
They knew nothing less than victory would do at Crowborough and their youngsters came up trumps.
Brighton struggled to 185 all out, Patrick Spencer top scoring with 57, with support from fellow teenagers Steven Ades (31) and Matt Prior (24).
Naeem Akhtar, the league's leading wicket taker, grabbed 4-58.
Crowborough collapsed to 91 all out, Chris Harrison as South African paceman Andy Sartor took 5-38.
Relegated Bexhill slumped to their tenth League defeat of the season when they lost by 80 runs at home to Eastbourne.
David Kirtley, younger brothers of the Sussex pace bowler James, hit 103 which included 17 fours and a six.
Mark Roughley (45) was top scorer as Bexhill tumbled to 128 all out in 39.4 overs as Paul Hacker took 6-58, his best figures of the season.
Chichester finish just above Bexhill but are safe because only one club is relegated this year.
They lost their final match by just three runs in an exciting finish at home to Horsham.
The visitors were dismissed for 145 as Nick Dyer took 4-24. Mark Nash, re-discovering his form and making a relatively rare appearance this season, took 4 9.
Abandoned: Three Bridges v Haywards Heath.
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