The Educational Institute of Scotland this week went public on the city's recruitment difficulties, pointing out that there are 31 long-term primary vacancies as well as many short-term gaps.
In secondary, there are said to be no available teachers for mathematics, music and physical education posts and senior staff have recently had to cover large groups in halls at Hillhead, Whitehill and St Roch's secondaries.
At Bannerman High, several departments have had to reorganise timetables because there were no teachers available to take classes in modern languages, chemistry, PE, English and support for learning.
Susan Quinn, EIS local chairperson, said: "Teachers' patience is exhausted on this matter. Glasgow must recruit more teachers and more permanent teachers quickly to prevent a rerun of this again next year."
George Gardner, the city's depute director of education, accepted this was one of the worst times of the year because of illness. It affected supply staff as much as permanent posts. It was also true that the supply pool dried up as the year progressed.
"We will be expanding significantly the size of our present supply pool in Glasgow but unfortunately it does not address the issue at this point in time," Mr Gardner said.
The EIS reveals that the city has only 36 primary and 18 secondaries teachers in its pool. Ms Quinn said the goodwill of staff was running out after four years of absence cover difficulties.
Dougie Mackie, EIS president, called on the Scottish Executive to act now to recruit and retain enough teachers to fill permanent, temporary and supply posts. With class contact time due to be reduced, the need for more teachers was more pressing than ever.
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