TEACHERS in public primary and secondary schools in Nigeria began an indefinite strike on Wednesday over unpaid salary arrears in most parts of the country. Their umbrella union, the Nigerian Union of Teachers, last week called on teachers to begin the strike if their salary and allowances are not paid before Wednesday. Last year, the Nigerian government fixed monthly minimum wage at 3500 naira ($37) but some of the 36 states of the federation complained of inability to pay the new wage. Some of the states are owing their workers, including teachers, at least six months in salary arrears.