Probation officers and social workers are not among those individuals specifically listed as mandatory members of the IEP team.  [20 U.S.C. Sec. 1414(d)(1)(B); 34 C.F.R. Sec.300.321; Cal. Ed. Code Sec. 56341.] However, if in the view of the person inviting them, they have special expertise or knowledge regarding your child; they can attend the IEP if invited by the school district or the surrogate parent. [Cal. Ed. Code Sec. 56341(b)(6).]