High Level Functioning Cognitive Ability

Hi everyone
We have recently been told our 5 year old son (kinder) is high level cognitive functioning, and is scheduled to undertake cognitive assessment (prior to starting prep in 2015). They are hoping to formally establish and identify the learning options for him in the school framework; accelerated learning options, Gateway etc. Have any other mums been down this path with pre school children and are there any downsides to starting school, given they get categorised in this 'gifted' arena? Any support groups around melbourne that assist parents with gifted children? Thanks in advance!