Tús - What should a caretaker/supervisor job entail?

Hi, would be grateful for any opinions on this:

My friend got a place on a Tús scheme as caretaker/supervisor, which in general involved painting and decorating, grass cutting etc. However he is now having to supervise children at an afterschool group as well. He queried this with his own supervisor who said he did not have to do it as it was not his job to do so, but the employer has stated that it is in his contract so he must do it. His contract only states his position as Caretaker/Supervisor. (When he took the placement he was led to believe that the position was a general handyman type role, supervising children was never mentioned)

So would the position/title of caretaker/supervisor cover supervision of Kids after school or should he take it up with his boss more formally?