CAPT OF A DC9 OVERSHOT ASSIGNED ALT DURING SID DEP EVEN AFTER THE FO GAVE SEVERAL ALT CALLOUTS.

Narrative

TFC AT PHX INTL WAS BUSY. CTLRS WERE LNDG AND DEPARTING TFC IN TIGHT SEQUENCE. OUR ACFT WAS POSITIONED ON THE RWY BEHIND A B737 STILL ON THE ROLL; WHILE ANOTHER ACFT WAS ON APPROX 3 MI FINAL. WE WERE ISSUED TKOF CLRNC WHILE PRIOR B737 WAS INITIATING ROTATION. WE WERE TOLD TO MAINTAIN VISUAL SEPARATION WITH THAT ACFT; AS IT WAS ON THE SAME SID AS OUR ACFT. OUR ALT CLRED TO WAS 8000 FT. I CALLED OUT AT 7000 FT '7000 FT FOR 8000 FT.' ENVIRONMENT WAS VERY BUSY. AT APPROX 7700 FT MSL; THE CAPT HAD NOT INITIATED LEVELOFF; AND ACFT WAS CLBING AT APPROX 4000 FPM. I TOLD THE CAPT '8000 FT IS OUR ALT' AS WE CLBED THROUGH IT. CAPT IMMEDIATELY INITIATED HARD LEVELOFF AND DSCNT; BUT WE CRESTED AT 8700 FT MSL. ATC ASKED ALT; ISSUED TA; AND HAD US CLB TO 10000 FT MSL. REST OF FLT WAS NORMAL. I BELIEVE THE VERY BUSY ENVIRONMENT; COUPLED WITH TIGHT SEQUENCING KEPT THE CAPT (PF) FROM NOTICING ALT OR HEARING MY ALT CALLOUTS. ATC HAS A DUTY TO MAINTAIN TFC FLOWS; HOWEVER; FLYING DEPS WITHIN 2 MI OF PRIOR TFC IS ASKING FOR TROUBLE.