The 15-year-old Spanish girl who arrived at Margaret's house 14 months ago didn't want to come to Ireland. But she quickly made friends with other Spanish students in various second-level schools around Dublin and had an active social life.

"In the beginning, there were a few nights when she didn't come back home until 2 a.m. I told her she couldn't do that, said `if you do go into Dublin, you have to ring us and tell us if you're going to be late, or if you miss the last bus'." After that, the year passed smoothly enough.

The organisation Margaret dealt with said: "treat them as your own". The basic rule, it advised, is that children should be home by midnight. But Margaret and her husband allowed their student rather more freedom than she would like her own daughter to have at the same age, believing that although she could insist on some basic rules, she couldn't have as much influence as she would with her own child.

Margaret knew, for example, that their student smoked - and believed she probably drank as well. "We told her she couldn't smoke in the house. As for the drinking, you'd know by the cans of beer on the patio after her friends had visited."

Margaret and her husband didn't worry overmuch about their student. She encouraged her to bring her friends around, just as she did with her own daughter, an only child. "I feel if you know who their friends are, if you're comfortable with their crowd, you're happier when they're out with them."

The student and her daughter were friendly, but attended different schools and had separate social lives. Wasn't this a potential problem for Margaret's daughter?

"It worked out okay. If my daughter was in the TV room with her friends, our student would just bring hers up to her room. In general, students do tend to defer to the teenager of the house. I suppose, though, that we're lucky in having quite a big house."

With an only child herself, Margaret wanted to to create more of a family atmosphere in her house. "It's good for our daughter to have to mix and share a bit, and, depending on the student, she actually does enjoy it. "I find it puts a bit of structure on family life. Before the student, it was hard to get my daughter to sit down for a family meal. Now I have a proper family meal for all of us at 7.30 p.m."

Margaret was paid £82 a week tax-free for hosting her student - but she doesn't think, in the end, that it really paid. "You eat better, you have a full meal every day; there'd always be yogurts in the fridge, and juice and bars and crisps for school. You wouldn't let things run out as you would with your own family, wouldn't be inclined to make a meal out of nothing - you feel you have an obligation to make them a proper dinner."

As anyone who has ever taken in students, however briefly, knows, when it works, it works - but when it doesn't, it can be torture. Cecilia and her family, for example, will never take in another Irish student from the country, after a bad experience a few years ago.

"The girl was 17, she was going to college and she had a disastrous effect on our family life."

Cecilia and her husband have three sons, who then ranged in age from 10 to 20. "I thought it would be nice to have a girl around the place. But she was an only child, and spoilt. She'd swan in at 1 a.m., and have a shower, noisily; she'd come home early and occupy the front room, watching TV; she'd roll up on the sofa and go asleep. She was responsible for paying the £60 a week due - and she never paid on time."

The result was that her own sons just kept to their own rooms, trying to avoid the student - and Cecilia's youngest son bitterly resented her presence. But for the opposition of her husband, who felt sorry for the girl, Cecilia would have asked her to leave by Christmas; instead, the agony dragged on until Easter - when Cecilia clearly, but diplomatically, made it clear that she couldn't have her back.

Since then, she's heard of similar bad experiences from friends - a girl who went "missing" en route from home to Dublin, who just didn't bother to ring either her own or her host family to tell them where she was, for example. Because Irish arrangements are usually not centrally organised in the way those for foreign students are, there is often no one to turn to for help when things go wrong.

The going rate for Irish students is about £60 a week, which Cecilia believes is not really economic.

Three years on, Cecilia and her family are still taking in students, but only foreign students. She gives her 14-year-old son an extra £5 a week pocket money when she has a student, as a kind of reward for his contribution to welcoming the student into the home - a sensible way to overcome initial grumbles. And she has learned, she says, to make the arrangement pay, by being a little bit more budget-conscious than she was when she started out taking students.