A320 CREW WAS TOLD BY ATC TO LEVEL AT FL330 WHEN THEY WERE PASSING FL340 FOR FL350 WITH A HIGH CLB RATE.

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CAPT WAS RELATIVELY NEW TO ACFT TYPE. AS FO; I HAD OVER 5 YRS AND 3300 HRS MORE TIME IN TYPE THAN HE DID. 4TH DAY OF 4 DAY TRIP AND HE WAS HANDLING ACFT EXTREMELY WELL. WE WERE CLBING OUT OF ATL. ATC CLRED US TO FL350. AS WE CLBED PAST APPROX FL280-FL290; WE ENCOUNTERED TURB. CAPT ELECTED TO EXPEDITE THE CLB. IN THE AIRBUS THIS FEATURE ALLOWS THE ACFT TO CLB AT BEST L/D SPD. THIS FEATURE ALSO RECALIBRATES WHEN THE ACFT WILL BEGIN LEVELING OFF. AS WE PASSED FL340; VERY FAST; ATC ASKED US TO LEVEL OFF AT FL330. INSTEAD OF LETTING THE ACFT STOP THE CLB AT FL350 THEN DSND; THE CAPT ACTIVATED THE 'ZERO VERT RATE' BUTTON. THIS ONCE AGAIN FORCED THE ACFT TO RECALIBRATE ITS LEVELOFF. THE AIRBUS ON AUTOPLT WILL TRY TO MAINTAIN ZERO G'S IN ANY MANEUVER. BECAUSE OF THIS; THE ACFT LEVELED OFF AT FL353. AS WE STARTED DSCNT BACK DOWN TO FL330; ATC REQUESTED WE STAY AT FL350. I REMINDED THE CAPT ABOUT THE EXPEDITE FEATURE; AND THE ZERO VERT SPD FEATURE AND HOW ALT LEVELOFF ARE RECALIBRATED. I AM ONLY THE COPLT; HOWEVER; AS THE 'MORE EXPERIENCED' AIRBUS PLT; I SHOULD HAVE BEEN MORE AGGRESSIVE AND SUGGESTED NOT USING THE ZERO VERT SPD BUTTON TO STOP AN EXPEDITE CLB.