Whenever a parent, educator or community member (such as a pediatrician) has a concern regarding the psycho-educational welfare of a child, then they can start the process of being considered for special education. According to federal laws, children who have measurable challenges can be considered and possibly recieve (if qualify) some degree of service from birth through age 21.
My middle child is 9 yrs. old and has had an IEP since the second grade and is currently in the third going on fourth. His individualized evaluation plan could not have been any better, especially in time for the PSSA's. He must have a proctor present to any exams except for his reading exams. But they can reword the question asked and he has no time limit. I make sure that is aware of this so he can learn to advocate for himself. I highly recommend a child gets evaluated as soon as possible so that the proper methods can take into place.
The younger the better for assessments! The longer a child must wait for someone to understand his needs, the more frustration he may find with school. Then its often difficult to see his true needs because the frustration or other behaviors "cloud the true issues".