TEACHERS have claimed the Education Department is risking a fall in education standards with its call for full-time teachers to take on extra part-time work to fill empty posts. They also have called for more parents to get involved in schools to ease their burden. The Governor, Mr Chris Patten, promised late last year that measures would be introduced to recruit 780 additional non-graduate teachers to work by September, as a step towards 2,200 new teaching posts by September 1997. Last Friday, the Education Department advised aided schools that measures to fill the demand for the 1993-94 school year included: Allowing full-time teachers to take extra shifts. Allowing primary and secondary schools to employ people with non-standard qualifications as permitted teachers after July 1. Immediately encouraging teachers due to retire at 60 to stay on, and extending service beyond 65. Immediately appointing retired teachers on a temporary, annual basis. Allowing schools to employ any number of part-time teachers on a temporary or regular basis. Primary schools can make offers after May 27, but secondary schools can appoint part-time teachers immediately. The Hongkong Professional Teachers' Union vice-president, Mr Au Pak-kuen, last night said proposals to lower entry standards or increase teachers' workloads could reduce the quality of education. He said the proposal to allow full-time teachers to take on extra part-time teaching up to 50 per cent of their full-time workload was ''unrealistic''. Primary school and especially secondary school teachers were already overloaded with teaching and non-teaching jobs, particularly given class sizes. ''The average teacher does not have the time and energy to do extra work or part-time teaching. I doubt the department will fill many gaps this way unless there are some teachers out there with the ability of a superman, but there might be some.'' He warned that those who took on extra work probably could not sustain educational standards. ''Teachers who work a full day already are exhausted. In mathematical terms it is obvious you will not perform as well if you take another part-time teaching load on top of your full-time work.'' Mr Au said teachers would prefer implementation of the Education Commission Report Five proposal that primary school teachers have their qualifications upgraded as a long-term measure. This was better than ''lowering the standard of entry qualifications and education''. He said appointment of people with non-standard qualifications should be limited to graduates with post-secondary diplomas from institutions such as Shue Yan College, Lingnan College or Baptist College, which were close to gaining degree-awarding status. Pay and training also should be improved to make the teaching profession more attractive. However, a short-term measure could be encouraging mothers to become teachers or school clerks at their children's schools, even if they did not need to work. ''Many of today's housewives are women who were university graduates or even teachers. If they take up jobs in the schools they can understand their child better, and help build up the teacher/parent relationship.'' Other mothers could help with clerical duties at schools to help ease the burden on teachers, and give them more time for teaching.