Let's make the law on age of consent simple – and not have draconian exceptions that presume abuse of authority where it doesn't exist! If there isn't an abuse of authority, then there is no victim and no point in wasting public funds on a prosecution.
Relatively recent law changes now mean that a teacher can be prosecuted for having a sexual relationship with a 16 or 17 year-old. Yet the age of consent is 16! Why should there be special rules for the teaching profession? Doctors and nurses aren't barred from having relationships with people who have been patients in their hospital. Police officers aren't banned from having sex with people who live on their beat. Tax inspectors aren't banned from french-kissing taxpayers!
Now, if a teacher abused their position, that would be a different matter. If they said to a sixth-former, "I'll fail you unless you give me a blow job," then that would be a clear abuse of their position – but prosecutors should have to show that some abuse of authority has actually taken place. The state should not presume that a relationship is abusive just because one partner is a student and the other is a teacher!
A person could marry a 16 year-old and then become a teacher at their school. They could already have a child together. Surely we can't prosecute them or ban them from being at the same school! And if we don't prosecute married couples, why should we discriminate against other couples who choose not to marry?