Have heard that these kids settle down and progress by the time they reach 10-11 years. Is it true?

My 7 year old son has autism. WE have mainstreamed him with a shadow. He is able to read and write and speaks clearly but speech is limited. We also have behaviour issues at school. Sometimes I wonder what I have gained by mainstreaming him. He is not able to grasp more than 50% of his cl academics at the same time, he is not that bad a case to be sent to special school. My mind is in a state of turmoil. DO these kids settle down and improve with time?