Teenagers do not know how to use basic kitchen equipment, and many cannot switch on a cooker or operate a can opener.

A survey of food technology and home economics teachers found that one in five teach pupils who are unfamiliar with basic household equipment used for cooking.

Almost as many reported that their pupils do not know how to clear away cookery equipment or wash dishes properly.

The survey of 330 teachers was carried out by Gill Elliott, of Cambridge Assessment, the Cambridge exam board’s research division. Her findings were reported at the annual British Educational Research Association conference last Friday.

Dr Elliott carried out her research following the Government’s announcement earlier this year, that every key stage 3 pupil will be given compulsory lessons in practical cookery from 2011. Many schools already offer practical cookery lessons for this age group. But the teachers who responded to Dr Elliott’s survey claim that these are rarely as effective as they could be.

Often, this is because they are working with teenagers whose knowledge of cookery skills and food is minimal. Fifteen per cent of teachers said that their pupils cannot recognise unprocessed food. For example, they are unaware that the chips they eat are made from potatoes. Others do not know the names of common vegetables.

A small number - 3 per cent - said pupils had no idea how to use chopping knives, or even cutlery.

Many of these findings were unsurprising, given that 12 per cent of teachers reported that pupils rarely witness cooking at home, and are not allowed to cook themselves.

And, while school cookery lessons can go some way towards remedying this situation, many teachers felt that they were severely limited by practical constraints. More than three-quarters believed that food lessons were too short: one in five said they were forced to teach in lessons of less than one hour. This meant that they were unable to cover bread-making, casseroling or roasting, techniques that require a significant amount of preparation and cooking time. Often, pupils were forced to work during breaks and lunchtimes.

Alternatively, staff had to take products out of the oven after the end of the lesson, or to weigh and measure ingredients for pupils beforehand. This, Dr Elliott points out “is both demotivating for the students and restricts some of the opportunities for learning”.

Similarly, many teachers are restricted by excessive class size. Sometimes four or more pupils are forced to share a single cooker. One teacher said she had only two domestic fridges to store the work of 46 pupils.

Some teachers get around this by splitting the class in two: one half cooks, while the other completes written work in another classroom. The disadvantage is that every cookery project takes twice as long, and pupils ultimately only receive half the practical experience they might otherwise.

Dr Elliott suggests that the problems of pupils’ inexperience and lack of lesson time might be addressed simultaneously. For example, if schools installed dishwashers, it would mimic the home environment and reduce clearing-up time.

“Teachers in this field are enthusiastic and keen to find solutions to the issues that they have raised,” she said. “But it must be considered whether schools alone should take all the responsibility for the education of students in these skills.

“Schools can only do so much, and if facilities do not exist . at home for students to practise their skills, then the process of educating them in this respect will always be limited.”