A teacher whose famous mother mysteriously disappeared when he was a child has been jailed after stabbing a school principal upon learning his contract wouldn't be renewed.Kim Ramchen was today sentenced to 15 months' imprisonment after admitting to intentionally causing injury, assault with a weapon and unlawful assault over the December 2 stabbing.He will be eligible for parole after eight months and 14 days, but having already spent 160 days in pre-sentence detention, could be released in August.READ MORE: Travel