Answer: No. This sounds like disability-based discrimination. Is the teacher requiring that all students in the class have a parent-chaperone or just your son? My guess is that your son has been singled out. If the teacher believes your son needs a 1-on-1 in order to safely attend the class field trip, the school must provide this accommodation. Having a 1-on-1 is a reasonable accommodation that allows your son to continue to learn in the Least Restrictive Environment (LRE).
If you believe the school is discriminating against your child, contact Massachusetts special education lawyer Lillian E. Wong today.