I would do two things. First, I would get the school special ed teacher involved and get some strategies as to how to reach this student. Hopefully, they can give you some ideas as to what works for the student. Second, I would find some small thing the student does correctly or appropriately and reinforce that behavior with praise as much I as I could. The more behaviors that can be positively reinforced the more the behaviors will become positive.

I have a student in my classroom who is special needs and demonstrates similar behaviors. One thing I would suggest is giving this student a desk that is away from the other students. This way, if he is compelled to hum or sing it won't be as distracting to the other students. I would also create an individualized behavior management plan with this student and use positive reinforcement to motivate the student to want to do well in the classroom setting. For example, if the student is not completing his work, I would tell him that if he completes all of his work that day, he can have some extra computer time at the end of class. If he is not showing respect to adults, I would model for the student how he should respond to adults and give him a check every time he shows an adult respect. This should also be rewarded with something that he likes.

The student may need to learn the appropriate behaviors in your classroom. You may need to teach lessons on social skills to the whole class. Everyone needs to practice appropriate classroom behavior. The student's classmates can demonstrate what is appropriate behavior and model it when the students misbehaves. Role play is a great strategy to integrate in the lessons to learn appropriate social behavior. It may take time, but it will benefit the student in the end and for future classmates and teachers as well. As the student learns the appropriate social skills, his ability to complete work and disrespect towards adults may decrease because he is more comfortable in the classroom.

In a classroom that I was interning in my teacher had a student that had problems staying on track and following directions and I was able to help by just connecting with the student. I just took a bit of extra time to learn more about the student and tried to phrase things differently so that he wanted to do the work or got excited. I would also try to talk to the school's special education teacher and see what more the school can do to help. Maybe the student needs an aid, this aid can also give them the attention that they need. You can also try finding out who the student's previous teacher was and try and see if they have any tips for you. I would also consider trying to talk to the parents and see if they have learned any tricks or have any helpful information, however this can be tricky because they parents can think that their child is in trouble and discipline the student. but maybe the parents can help you create an incentive program that follows into their home life. such as if the students follows the rules and does their work they get to do something special at home like extra TV time or ipad time.

Have little queues to keep the student on track. Have something that represents when he needs to contain himself and when something is not appropriate for that moment.

I think that you should consult the student's IEP to figure out what type of accommodations are in place for this student. You could be missing something that should be implemented for this student that allows for the humming or singing. The refusal to complete work is something that the teacher will have to tackle. Maybe thinking of some sort of incentive program to motivate the student could help. It is important to take the time to explain the rules and procedures of the classroom so the student has an understanding of how he is supposed to act. He also needs to be made aware of the consequences for exhibiting such negative behaviors.

There definitely needs to be an IEP in place for this student in order for him to keep on track with his goals. His behavior may be disrupting the general ed classroom but sometimes students with special needs have trouble understanding their behavior and how it is affecting others. An IEP will give both the student, his teachers, and parents a way to understand, communicate, and address these issues.

Speaking with the student's special ed teacher is extremely helpful since they are trained to work with those students and know how to react to the behavior and handle the situation for the most part. Also try to reinforce his good behavior, this could help the student understand that you are not a threat or someone who only cares about the bad things students do.