CRB Checks - allowable cost?

I have been asked a question by a school burser about whether a self employed teacher can claim tax relief on the cost of the CRB check required to enable them to work.

The teacher is peripatetic and the school is merely providing the facilities for the lessons, which are paid for directly by the parents to the teacher.  The school does not charge any rent for the facilities, and hence is not making any money from the arrangements.  The school is, however, legally bound to obtain CRB clearance for this teacher, and has passed the cost on to him. 

Has anyone experienced resistence from HMRC to allowing the teacher tax relief on the CRB check?