sleeping with an underage student is a rape (of course I'm thinking Poland here). A 14 year old
In the UK, that would be under 18, if one party is a Teacher, Youth Worker, Clergy etc. 16 normally, 18 if one party is in a position of responsibility or if money changes hands.
It happened to a guy I was at school with who became a Teacher. I'd not thought about him for years, then his face was all over the news having eloped with a pupil. She was over 16 then, and AFAIK that was one of the cases that led the government to raise the age to 18 in those situations.