Schooldays are the happiest days of your life, right? Not according to BBC news reports. "Too stressed to go to school", "Stress threat to school exams" and "Exam overload stressing pupils" are a few of the doom-laden headlines to be found on its website, which doesn't do much to bolster my confidence as I walk up to the Royal High in Edinburgh on my first day as an adult pupil.
I've been studying Spanish for four years and the Royal High, in its wisdom, has allowed me to join the Advanced Higher course.
A bowlful of goldfish are swimming around in my stomach as I walk into class for the first time. I'm over 40 and though I've been in schools - I'm an adult education creative writing tutor - it's a long time since I've been a school pupil.
The teacher smiles and welcomes me in elegant Spanish. My sixth-form classmates, Morag - the head girl - and Katie, smile too. We ease ourselves into the term with some Spanish conversation and a video, and soon it's just another Spanish class.
Schooldays, to me, used to mean the shrilling of the bell, the watery cabbage scent that pervaded the dining hall and the squeak of chalk on blackboard. In the newly refurbished Royal High, the bell no longer shrills but emits a tasteful, two-tone hoot, there is no scent of cabbage - or, indeed, anything - and blackboards have been replaced with whiteboards, making chalk a thing of the past.
We start to read the play Bodas de Sangre (Blood Weddings) by Federico Garc!a Lorca. It's a mixture of realism and surrealism, chock-full of symbolism and metaphor. Writers' heaven.
"I've auditioned for The Secret Policeman's Ball," Morag tells us after class, referring to the Royal High's annual variety show in aid of Amnesty International. "Don't think I'll get a part, though."
Coming out of class, I run into my son - he's in fourth year - in the corridor. His eyes glint with recognition for a millisecond before his head whips around and he starts talking to his companion. Am I hurt at this lack of recognition? No. I've been well-drilled. "If I meet you in school, Mum, you're not my mother."
I ask Morag if she got a part in The Secret Policeman's Ball.
"I got two," she grins.
"Are you in it, too?" I ask Katie.
"No. I can't do it," she says. "I'm too busy. I play four instruments, you see."
I'm really getting into Bodas de Sangre. It's beginning to seem normal to inhabit a terrain where none of the characters bar one has a name, death is a woman and the moon thirsts for blood.
Our teacher leaves. Walking into our new teacher's classroom for the first time, it's first day nerves all over again.
It seems my fame has gone before me. "Welcome, Mrs Crosbie," he beams.
"It's Katrina," I say firmly. I want to be respected in the school, but because of what I do, not who I am.
We're now in a composite class with Higher Spanish. We outnumber them three to two and we have an ace up our sleeve. Pilar, a smiling young woman from Barcelona, is the new Spanish assistant and from now on we'll have her for two blocks a week.
The fact that the class is composite doesn't cause any problems. The Higher Spanish girls sit at the front and we sit at the back and, given that there are only five of us, we co-exist peacefully.
Morag now has four parts in The Secret Policeman's Ball.
The head of modern languages tells me that the school is happy to run Spanish classes for such small numbers.
"These pupils have given a lot to us," she says. "They've worked hard as they've moved up through the ranks. We're delighted to be able to give something back."
Morag now has seven parts in The Secret Policeman's Ball and is rehearsing day and night. "I live here," she announces one morning, yawning. "I'll have to bring in a sleeping bag."
But she's coping: her work isn't suffering.
And oughtn't school to be more than just verbs and theorems?
Our teacher gives us our Advanced Higher Spanish handbooks, which detail the topics - the environment, the media, family life - we will be examined on.
"We'll have to move on from the play soon," he warns.
That's bad, because I've fallen in love with Federico Garc!a Lorca. OK, he was gay and died nearly 70 years ago, but there's nothing to stop me starting to write a novel about him, is there?
We are going to study a film next, Carlos Saura's AAy, Carmela! A sortie on the internet informs me that it is a tragi-comedy with satirical overtones.
That's work? When I was growing up in Glasgow you couldn't find anywhere to go and see foreign films, never mind watch them at school.
Standing at a first-floor window during break, I watch a group of first-year boys in the playground, rough-housing, pushing and shoving until - it's not deliberate - one of them falls to the ground. By the time he gets up, clutching his elbow, all the boys except one have drifted away.
His friend puts an arm around his shoulders and leads him towards the doors.
I watch the injured boy as he blinks back the tears, a brave soldier in a world where masculinity equals impassivity and emotion is a foreign country populated exclusively by girls. Finally, he can't help but cry.
I want to cry, too, but I force myself not to. Remember the drill, Katrina.
Here, you leave your motherhood at the door.
I walk up the silent, tree-lined driveway to the school. There is a whisper of breeze, a flash of black and white as a magpie preens itself on a branch. Through the plate-glass doors I go, pausing just long enough to return the janitor's cheery "Hello", and head up the back stairs.
The classroom is empty: Morag is off and Katie is away on a field trip. I place my bag on its usual chair, take my dictionary from the shelf and sit, waiting for our teacher. A ray of sun slants through the blinds. The classroom is lit-up, golden, beautiful.
Maybe schooldays really are the happiest days of your life.