Is it permissible to operate a ceiling fan at school and use an electric kettle to make tea, knowing that there is no work and he agreed to this during the summer?

The answer is summarized in the following points:

It is permissible to use the school's electricity for personal needs if explicitly authorized by the responsible authority or if it is customary to do so, within the usual limits. It is permissible to use the fan, as it was provided for the employee's need, and one cannot stay without it during hot weather.