Have I had enough Tetanus jabs?

If the jab you had at school contained tetanus - it ususually does - then that means you've had five in your lifetime so are covered.

You should have good levels of immunity now, but they recommend boosters every 10 years particularly if your in a job that puts you at risk.

If you're in the USA, Laroxe is correct. a Td (Tetanus/Diphtheria) booster is recommended every ten years - and more recently, it's advised to substitute one of those with a Tdap (tetanus/diphtheria/pertussis) booster to boost your pertussis (whooping cough) antibodies. (And, for pregnant women, a Tdap booster is recommended every pregnancy).  If you're in the UK or another country, the vaccination schedule may be different. The 3 DTP's you had were the initial series of shots to give you immunity. The DT you received and any other shots that included tetanus in them were boosters. You received four doses of polio vaccine so you have completed the series. An adult polio booster would be recommended if you were to travel to a country that still experienced polio outbreaks.