Its proberly more like what the employer dosn't want to hear.
After IR35 all the rules about running a limited company changed along with some of the self employed rules.
The tax man takes a very dim view of employers making workers have self employed status when they are actually working day in and out in the same job. They look on it as the employer is avoiding their employers NI contributions.
After you start get a m8 to phone the tax office and pretend to be thinking about working for the company and ask about self employed status. The tax man will be down there pretty quick for an audit.
The down side of this is they will proberly be stung for the last 3 years of NI contributions for all self employed instructing staff.
There are also issues being self employed which means you have to personally carry public liability insurance etc etc. If you are employed by the school there insurance covers you.
Being self employed puts you out on a limb with both the tax man and if anything happens. I never worked self employed because the companys had all been advised by there accountants that they would be shafted if found out big style.
MJ