CL65 FO FAILED TO CROSS MANDATORY FIX DURING APCH TRANSITION TO IAH.

Narrative

ENRTE TO IAH; I PROGRAMMED THE FMS FOR THE ILS RWY 27 INCLUDING ALL ASSOCIATED STEP-DOWN FIXES AND THEIR MANDATORY XING ALTS. THE FO AND I DISCUSSED THIS INFO ENRTE AND AGAIN AS PART OF THE APCH BRIEFING. I ALSO EXPLAINED THAT THE MANDATORY XING ALTS AND GS ARE NOT COINCIDENT. APCHING IAH; OUR FLT WAS HDG 180 DEGS AT 3000 FT AND 180 KIAS ASSIGNED. ATC ISSUED A HDG OF 240 DEGS AND TOLD US TO INTERCEPT THE RWY 27 LOC. INTERCEPT OCCURRED APPROX 2.5 NM E OF FESTA. THE MANDATORY XING ALT AT FESTA IS 2000 FT. I CALLED ATC REQUESTING LOWER. ATC TOLD US TO MAINTAIN 2000 FT UNTIL ESTABLISHED; CLRED ILS RWY 27 APCH. THE FO ARMED APCH MODE WITH THE AUTOPLT ENGAGED. AT THAT POINT; WE WERE 30 SECONDS AND 1.5 NM E OF FESTA AT 3000 FT AND ABOVE THE GS. I SELECTED VERT SPD 3400 FPM DOWN IN AN ATTEMPT TO CROSS FESTA AT 2000 FT BUT OUR DSCNT ANGLE INTERSECTED THE GS CAUSING THE AUTOPLT; WITH APCH MODE ARMED; TO CAPTURE THE GS THEREBY SHALLOWING OUR DSCNT RATE AND CAUSING US TO CROSS FESTA ABOVE 2000 FT. I ATTEMPTED TO CORRECT THIS BUT DID NOT HAVE ENOUGH TIME. ATC MADE NO COMPLAINTS AND TCASII WAS NOT A FACTOR. DESPITE OUR EFFORTS TO PREBRIEF; THE MANNER IN WHICH ATC VECTORED US FOR THE APCH APPEARED TO CATCH THE FO OFF-GUARD. THIS MAY HAVE BEEN DUE IN PART TO HIS LIMITED AMOUNT OF PLTING EXPERIENCE AND ESPECIALLY HIS LIMITED EXPERIENCE IN THE CL65.