Clare Jack explains why she felt compelled to give up her career to be at home with her daughters now that they have reached secondary school age, while Cassandra Jardine says mothers of teenagers might find they are not needed as much as they fondly imagine

‘I don't know how you do it.” During the 13 years that I have spent building up my career as a public sector management consultant, that is the phrase I have heard applied most frequently to my insane daily juggling of work, children, home and husband. No one seemed to realise that I didn't know either.

Well, now I've decided not to do it any more – and I am not alone. I am the third middleaged mum I have heard of this week who is giving up an exciting, satisfying, seriously big-salary job for these reasons, and I suspect there will be more of us fortysomething mums with demanding jobs coming to the conclusion that in a family, two big jobs + teenagers = impossible.

The key word here is ‘teenagers’ and just how much parent time they need. Strangely, that's the bit that has never been discussed in all the acres of articles I've read in the past 13 years about combining work and children.

Experts tell you that it's consistent, loving care an infant needs – and, mercifully, that it doesn't matter whether it's from you – and talk you through the traumas (for you and your child) of starting primaryschool. But having babies and working, or having primary schoolaged children and pursuing your career, are both easy-peasy compared with what happens when your child walks through the gate of their secondary school.

Suddenly there's homework almost every night, there are sports clubs and matches several times a week, there's the friendship angst (I have two girls, so replace with geek angst if you have boys), there's the puberty angst.

Out of nowhere they hate you and love you in equal, ear-splitting measure several times a week. Added to that are the exams – every term, it seems – during which you have to bear the pain of them learning what revision is for and ringing you up, at work, in tears, because they have just flunked maths. That really makes you feel like a rubbish mammy.

Their needs are immense and ever-growing and you're not there to help them through it.

That's a massive guilt trip. It generates a terrible angst in you; the fear is that you are not contributing to what they should, or could be, as they deserve.

How to survive the juggling act? We thought au pairs would do the trick: young women near to the girls' ages who would relate to them. We liked them, the kids loved them, but the stress of seeing a Turkish au pair, who was closer to the children's age than mine, try to help with English homework was painful. That's what finally brought me to my decision.

Teenagers are hard, hard work even if they are pretty normal, apply themselves at school and are reasonably well balanced.

Now is when they need me, which they didn't when they were tots. Anyone can look after small children; only parents can look after teenagers.

They need the support, the confidence-building, the tear-drying, the taxi-service, the mine of useful information, the books you've read, the experiences you've had.

So I have decided to pack in the big job and become a full-time mum at 45, having worked since I left university at 21. My husband, a construction consultant, Laura, 13, and Isabel, 11, are delighted.

I'm looking forward to it and am terrified at the same time; it's not about loss of money or status, it's about succeeding in a new career.

This isn't about downsizing and moving out of the big smoke to a country idyll either. This is about having a normal domestic life for the first time in our history as a family – I wonder if we will cope.

- Clare Jack

'Whenever I hear of a woman giving up work to spend more time with her older children, I give her a year. After 12 months of full-time domesticity, the born-again homemaker has invariably signed up for an art foundation course or taken up psychotherapy.

It’s not that she didn’t sincerely mean to concentrate full time on easing her teenagers’ path to wellbalanced adulthood but that, once she had parked her briefcase, she discovered that she was not needed as much as she fondly imagined.

According to Parkinson’s Law, a task can expand to fit the time available, but even if you take the most leisurely approach you cannot make a full-time job out of looking after teenagers. Once children start secondary school they aren’t just physically absent from the home more of the time, they begin a private, psychological retreat from which anyone who isn’t their own age is barred.

Sometimes, when I happen (despite my full-time job) to be at home at teatime, I bound through the front door, eager for quality mothering time with one of my five children. “Cooooeee, I’m home,” I yell, ready to act as a sounding board for their moral dilemmas and to share my limited knowledge of the causes of the First World War. Echoing silence follows.

After a few minutes I realise, yet again, that what my three teenagers really want is for me to get on with my own life, with the proviso that I am available on fastresponse should they need to let off steam about the French teacher/best friend/urgent desire to eat salmon fillets for dinner. The vast majority of this can be done at the end of a phone. Or it can wait until I get home.

Waiting is good for teenagers. So is learning to be self-sufficient. If I were at home all day I wouldn’t be able to bear the levels of mess in their bedrooms and would sneak in to tidy up – probably reading their private diaries in the process.

I also know that, in order to feel useful and wanted, I would act as an all-hours taxi service. Since I’m not around, they are learning the hard way that elves don’t pick their knickers off the floor, that homework is not intended to be a collaborative effort, and that if they want brownies they had better find a recipe and follow it.

‘I need a lift’ is still a sentence I hear far too often but, reluctantly, even the most princess-like of my children are discovering that those big, red vehicles on the road are buses, and that Dart trains aren’t scary.

Of course, there are dangers to travelling around unaccompanied, especially if you live – as we do – in the city. Last weekend, a drunk waved a knife at one of my girls who was with a group of friends. It did her good.

Paradoxically, she is now much less worried about the threat of mugging because she faced it and coped.

Right, you may think, you’ve got my number: I’m one of those emotionally bankrupt remote-control mums who thinks she is being a mother when in fact she is just the family administrator.

Maybe you are right, but a little independence from their parents is what children both want and need, so long as you are around to dry their tears and hear their fears.

Like most working women, I have often wished I had been able to spend more time at home with my children. I would have loved to have had longer with them when they were tiny, and it would have been delightful to have had more opportunity to stand and stare into puddles with them as toddlers.

I didn’t because we couldn’t afford it. Neither my husband nor I have what are called ‘big jobs’, but the advantage of that is that neither of us is working 16- hour days or travelling for half the year. We are both around enough for grumpy teenagers to feel there is always one of us available, whether to act as an emotional punch-bag or to hear their news.

When women say they are giving up work to spend more time with their older children, often what they mean is that they want a break and a change, but they can give themselves permission to do so only if they couch their choice in self-sacrificial terms.

For a short while it will be heaven. After that, I wish them well with their choice of second career.

- Cassandra Jardine

- Clare Jack