ACR ACFT ALT OVERSHOT DURING DEP CLB.

Narrative

DEPARTING ONTARIO ARPT WE WERE GIVEN INSTRUCTIONS FROM ONTARIO DEP TO LEVEL OFF AT 6000 FT DUE TO TFC AT 12 O'CLOCK. THE FO WAS FLYING THE ACFT. AS WE WERE CLBING THROUGH ABOUT 4500 FT AT A RATE OF ABOUT 3500 FPM; THE FO ENGAGED THE AUTOPLT. AT ABOUT THE SAME TIME; THE TCASII HAD INFORMED US THAT THERE WAS INDEED TFC AT 12 O'CLOCK. AS WE WERE CLBING THROUGH 5000 FT; I NOTICED THAT THE AUTOPLT STATUS DISPLAY INDICATED THAT THE AUTOPLT HAD ACQUIRED THE LEVEL OFF ALT OF 6000 FT. I WAS LOCATING THE TFC AT 12 O'CLOCK VISUALLY AND CAME BACK INSIDE THE COCKPIT AND NOTICED THAT THE AUTOPLT FAILED TO CAPTURE THE DESIGNATED ALT OF 6000 FT. I IMMEDIATELY TOOK CTL OF THE ACFT AS WE WERE PASSING 6000 FT. FORTUNATELY WE WERE NOW CLBING AT A RATE OF 1000 FPM AND WAS ABLE TO STOP THE CLB AND BEGIN AN IMMEDIATE DSCNT PRIOR TO CLBING THROUGH 6300 FT. WE WERE LEVEL AT 6000 FEET IN A MATTER OF 3-4 SECONDS. THERE WERE SEVERAL CAUSES TO THIS SITUATION. AS A NEW CAPT FLYING WITH A BRAND NEW FO; I SHOULD HAVE KEPT A CLOSER EYE ON MY FO'S FLYING. WE ALSO DISCUSSED ENGAGING THE AUTOPLT EARLIER IN HIGH TFC AREAS SO BOTH PLTS CAN SCAN INSIDE AND OUTSIDE THE COCKPIT