On a dusty highway in open country outside Kabul, a class of young girls, heads covered with hijabs, are being put through their paces in a primary school. It is a scene replicated around the world. The difference is that in Afghanistan a few years ago it would have been unthinkable. The Taliban refused to allow it. Now the feeling of hope is palpable. The girls, none of them older than seven, are already raising their sights beyond the wildest dreams of their mothers. I asked them if they wanted to work when they grew up. The answer, overwhelmingly, was yes. One wanted to be a doctor, another a teacher, a third hoped to break into the all-male ranks of the Afghan police.

I thought of my own mother and my grandmother, both pioneering female doctors. I thought, too, of my own daughter, due to start school in September, and our perhaps casual assumption that ahead lies secondary school, perhaps university and, if all goes to plan, a well paid job. The education system that we take for granted in Britain is still a distant dream here, where the government struggles to find teachers and classrooms. But the girls at the Qala-e-Baig school in Shakar Darra are among 2m attending schools across the country. They are a visible sign of real progress.

When the Taliban fell in 2001 there were only 900,000 children in school, all of them boys. That figure is now 6m and rising. Five million refugees have returned home and 82% of the population have access to healthcare, nine times the figure in 2002. But let me also admit that there is a very long way to go. Afghanistan is the fifth poorest country in the world. One in five children dies before their fifth birthday. Millions are malnourished.

The signs of conflict, new and old, are everywhere. A few hundred miles south of Kabul, I visited a very different school. Its empty shell stood forlorn and deserted, the walls pockmarked by bullets and a mortar shell hole in its roof. The school at Garmsir, in battle-ravaged Helmand, has not seen children or teachers for many months. The town was taken back from Taliban insurgents in May. Only now is life reverting to normality. A doctor is trying to operate in a clinic stripped of all its equipment and there are plans to refurbish the school.

Elsewhere in Afghanistan it is a more sombre story. The minister for education told me that another teacher had been beheaded by the Taliban in the past week. Schools are burnt down and the populace terrorised. That kind of brutality makes the British presence so necessary. The toll is high: 13 British soldiers have died in the past three weeks. Yet in the words of Des Browne, the defence secretary, the troops of the 38-nation coalition are here in a “noble cause”.

At the British base at Lashkar Gah I met soldiers from my Paisley constituency. Most were young, working-class lads barely out of their teens, 3,000 miles from home and a million miles beyond any familiar experience. Their morale and their sheer bloody resilience were remarkable. Through the summer they are patrolling in furnace-like heat routinely topping 50C. Garmsir, translated literally, means “too much heat”.

The front line is now just as likely to be a marketplace as an entrenched position in the countryside. Gone are the set-piece battles, to be replaced by the tactics often seen in Iraq: roadside explosions, suicide bombs and mines. Through it all, our servicemen and women endure. In the words of one soldier: “All we want is a bit of recognition. If you see a squaddie in desert fatigues walking through your local airport or train station, go up and say hello, tell them they’re doing a good job. It doesn’t cost you anything but it makes the world of difference to us.”

There is little doubt that British forces are making real strides but the message to me, again and again, was that without security there can be no return to normal life. Progress is being made in cutting the number of provinces that harvest the poppies which provide the heroin on our streets. And we are seeing signs that where farmers no longer feel intimidated, they are happy to switch from poppy to wheat or saffron. Narcotics dealing and bribery, however, remain rife – issues I raised personally with President Hamid Karzai – and moves to tackle them have proved inadequate. Put on top of that the poverty, the lack of basic local and central government structures and the tiny tax take and you have a set of challenges that individually would test many stronger states. That is why the development effort in Afghanistan will take decades.

Seventy-two hours before I left the UK, I met dozens of veterans of previous wars at an event in Paisley. For them, service and sacrifice were a mercifully distant memory. For a new generation they are a daily reality. Their courage is laying the foundations for a brighter future for the girls I met at Qala-e-Baig and children like them across Afghanistan.

Douglas Alexander is secretary of state for international development

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