I reckon in the old days, when I was young, being a teacher was a good job and window cleaning was not as lucrative as it is today.
Nowadays, I can only imagine that teaching is very stressful and much less rewarding with massive amounts of paperwork, red tape, government intervention, ofsted targets and reports, teaching assistants blah blah etc etc.
And window cleaning is...shall we say more lucrative, with much less stress.
Mick, if cleaning doesn't work you can always do a teaching course and teach English as a foreign language abroad.