I never went to sleep school but went to a day service run by child and youth health. Sleep school has an added benefit that if it works while there, you get a chance to reset his natural sleep rhythms. At the moment he's perpetually overtired from not getting enough sleep. Sleep school should give him the sleep he needs while you're there. Then when you get home, you won't have an overtired baby that you can get into a nice little routine that should help.
Have you gone on the cancellation list? Also the good thing about sleep school is they have paediatricians who rule out any health or medical issues first as sleep training won't wit if there's an underlying health issue. Am I right in saying he hasn't been to a paediatrician yet? I can't remember.