i strongly urge you to do adv eng. i was in standard for all of yr eleven and first term yr12 until my physics teacher of all people found out i was doing standard, and she panicked for my atar (she is the best teacher ive ever had and she knows her shit. she was even offered a job at usyd to lecture phys but rejected it cos she is the best). i found that it is much easier to get higher marks in advanced than it is in standard, believe it or not. and this generally stands true in the hsc cos the people who do adv get the band 5's and 6's.
do your atar a favour and move up asap