change in behavior and school work

I have a 10 year old son who until this year has been very caring, loving, respectful and helpful, he has been doing very well at school, for the last two years he has been in the top 1% of Queensland for a national maths test and last year was in an advanced class.  This year there is no advanced class.  He is not trying at school at all, he had a maths test recently and got 30 right out of 46. He begged and begged to learn the trombone and does not even want to practice.  He does not want to do his homework at all and does not want to go to school. When asked why this is the case he says he is bored,  however his teacher says he gets lots of answers wrong and she is not able to give him any advanced work because he is average.
Can you give any advise, we are getting lots of back chat and whining and tears.

[margypops]

It does sound as if there could be a problem at school, perhaps ask him pertinent questions ,like 'Have you any friends at school and 'how was teacher today, there will be a reason he is doing this, something at school is upsetting him, as he doesnt want to go, I wonder if the teacher has any attitude in front of the class.regarding him getting answers wrong ?  

[Sandman2]

    It is possible that he is highly bored and (thus) has turned off.  It is possible that the teacher (or the system) does a lot of "drill and kill" at this level.  If its the stuff your son "gets" instantly, then it may be hard for him to see why he has to do it.For the teacher to say she can't give him any advanced work is BS.  He was advanced before he got into her class.  It may be too late to do much for this year.   However, I would definitely talk to your principal (headmaster?) and show him/her (bring proof) how well your son did the two prior years.  You are having this meeting because you don't want the same thing to happen next year.  You might also talk to a few of the parents in your sons class to see how things are going with their kids.
    Another thing to do is to look at his last test.  Are the mistakes due to careless errors perhaps caused by working too fast, are are they mistakes due to not understanding how to do the problem.  If his mistakes (and the same goes for homework) are of the careless variety, that is one thing and can be fixed.  If the mistakes are because he doesn't know how to do the material - that is much more serious.  Especially in math which is cumulative knowledge.  Then its the question of what is causing him not to learn new material.  Some sharp kids just think they will get it like always and don't realize till too late that they should have been paying attention. Many times this is self correcting, but it is correctable.  However, if he is not getting the material because he is having trouble focusing (and for intelligent kids, it starts to show up academically about fourth or fifth grade in math),  then you have a whole different problem on your hands.  It do can be dealt with - but it takes a lot more effort.
  There are two other things you really need to do.
One- he has to do his homework.  No excuses.  It doesn't matter if he hates the school or the teacher or the work.  It has to be done.  It's called homework not funwork for a reason.
Two - and this is the most important- you need (at least for a while) to help him do it.  This will quickly tell you if he as trouble focusing, etc.  If he can crank through the work without batting an eyelash, then you have good information to talk to the principal about next year.  If he starts, stops, loses focus, gets frustrated...then its a different ball game.
    By the way if he is a very intelligent kid he has learned coping mechanisms that he will subconsciously use to hid his problems.  So it might take you awhile to find out what is going on.   Good luck and keep us posted.