This frequently asked question was addressed in the February 2020 issue of the Office of Special Education Programs (OSEP) update. Read below for the answer from OSEP:
While there is nothing in the Individuals with Disabilities Education Act (IDEA) that would prevent a State from requiring parental consent for age appropriate transition assessments related to appropriate measurable postsecondary goals, it is the position of OSEP that in general, IDEA does not require a public agency to obtain parental consent before conducting those assessments, unless the assessments are part of an initial evaluation or reevaluation. We believe that generally, parental consent is not required prior to conducting an age appropriate transition assessment because the purpose of the assessment is to develop appropriate postsecondary IEP goals and not to determine whether a child has or continues to have a disability, and the nature and extent of the special education and related services that the child needs. If, however, the IEP Team determines that a reevaluation of the child is warranted in order to obtain additional data, based on the student's educational or related services needs including improved academic achievement and functional performance, the public agency is required to obtain parental consent consistent with 34 C.F.R. § 300.300(c).