Consider all options
There is rarely anything such as a "free lunch" so you will need to enquire closely what is on offer. If it is a boarding school, and the accommodation was offered as part of a requirement for extra duties, your contract would need to specify this. Alternatively, it could be a benefit in kind and, therefore, taxable. As to whether or not it is good to live on top of the job, only you can decide. The time saved travelling is a good thing; you have more time with your own children. However, the risk is that you are always on show. But, it may be no worse that meeting your pupils in the supermarket every week. If the school is offering you reduced fees for your own children, you will need to consider whether there are any tax implications in the benefit you receive.
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