No. You have the right to go to school full time. In fact, there is a law called the Education and Training Reform Act that children must go to school full time until they are 17 years old.
Sometimes, if there is only funding for a part-time aide, a school might tells the student who needs the aide that they can only come when the aide is available.
The school is not allowed to do this. They also do not have the right to tell you that you should be at school part time. You have the right to attend school full time just like anybody else does.
On the other hand, there may be a situation where you can’t attend full time because of your disability. For example you might have a disability such as Chronic Fatigue Syndrome, or another disability where you can only manage a few hours at school at a time. If this is the case, you can get your doctor to write a letter explaining this. The school or other education provider must take notice of the doctor.