It is not that long ago that primary and secondary schools were like two countries with a rugged border between them that only children could cross. Even today, when the educational importance of smoothing their passage has been widely recognised, prolonged and meaningful adult contact across the divide is unusual.
It is also, say the handful of teachers who have made the journey, some of the best continuing professional development they have ever had.
"I've learnt so much from watching other teachers," says Kara Skelton, a primary teacher now in her second year in the English department at Auchinleck Academy in East Ayrshire.
"At first I just observed and it was all a bit strange: having the same kids for an hour before they moved on; teaching just one subject. I was a bit worried I wasn't going to be able to do it.
"But quite quickly I started thinking 'This is 5-14. I can do that', and I started joining in and doing co-operative teaching."
Teaching solo came later, as it did for other East Ayrshire teachers working across the primary-secondary divide as part of a Scottish Executive-funded Future Learning and Teaching project. "It's in its second year now and we've just heard we've funding for a further year," says early years co-ordinator Hilary MacGillivray.
"The project has three aims: to raise attainment, reduce class sizes and make the transition from primary to secondary smoother and more productive."
Four secondary schools and their associated primaries are participating, with the project paying the salaries of an additional primary and secondary teacher based in each learning partnership. Maths is the focus in two of these communities, English in the other two.
"The secondary teacher goes into the primaries to teach, while the primary teachers are based in the secondary school, where they teach S1 and S2 classes," explains Ms MacGillivray.
"The primary teacher also goes into the associated primary schools to release colleagues to come to the secondary and teach co-operatively. It's quite complex, but it's working well."
Initial misgivings of teachers from both sectors took time to be allayed, says Donna Kirkwood, a primary teacher based with the maths department at Grange Academy in Kilmarnock.
"At early meetings the primary and secondary teachers kept themselves to themselves and sat in separate groups. Now they all mix together, and not just primary with secondary. People from the different primaries have got to know each other and are working together, which is very useful, especially for developing common programmes of study."
The improved relationships and common programmes will be lasting benefits, say the teachers.
"It's not just better relationships with our primary colleagues," says maths teacher Steve Taylor, who is teaching in Grange Academy's associated primary schools. "There are the kids too. I can be in the supermarket and primary pupils will come up and say 'Hi there, Dr Taylor'. It means there is a friendly face when they come up to secondary school."
It is an important point, says Ms Kirkwood. "A lot of primary kids have told me they're not as worried now about going to secondary school because the teachers aren't as scary as they thought."
One of the most obvious outcomes of the project has been the adoption of the primary classroom appearance in the secondary schools. At Grange and Auchinleck academies, cartoon characters, key messages and colourful samples of pupils' work now adorn the walls.
Compared to a primary school, Auchinleck Academy's classroom walls seemed drab, says Ms Skelton, who worked the miracle. "It took me a wee while to pluck up the courage to suggest putting up a few things." The favourable response from pupils and teachers encouraged her to do more.
"It's lovely isn't it?" says Mary Byrne, the principal teacher of English at Auchinleck Academy. "It's bright and cheerful and the kids love it.
They're now coming to us with their own suggestions."
Colourful wall displays are spreading to classrooms beyond the English department as teachers drop in and go away with fresh ideas. "It's happening all over the school," says Ms Byrne.
Less evident but equally startling changes have been taking place in the teachers, as observation and co-operative teaching suggest new content, methodology and styles of teaching.
"The project creates classes of 20 rather than 30, so we have more time for each pupil," says Ms Byrne. "That and Kara's teaching methods are a big help, to less able kids in particular. In reading, for instance, we do a lot of textual and critical analysis in the secondary. Outside learning support we never used to do much word recognition, spelling or phonics. Now we do."
Ms Skelton, in turn, will take back to primary school a deeper understanding of how to teach English, particularly writing.
"I used to find it hard to get ideas going and always felt under pressure to get the kids to produce something every lesson. Now I know you can take more time, build things up, produce something at the end of several lessons.
"I understand better how to teach writing because I've been watching so many teachers and different ways they go about it."
Dr Taylor has gained respect for his primary colleagues and the range of skills they bring to the job. "I'm impressed by the amount of preparation, the way they handle mixed ability groups and break things down for them, and the interactive methods they use to teach maths," he says. "I'll be bringing that back to the secondary. It gets the kids involved, makes maths enjoyable for them."
Learning standard methods of setting out answers will benefit primary pupils when they come to secondary school, he says, while his use of information technology in class has been motivating primary colleagues.
"When they see how kids respond to interactive whiteboards and computer presentations, they're keen to learn."
The project is delivering new perspectives and highly effective professional development, says Ms Kirkwood, while the pupils are benefiting from continuity of resources, methodology and programmes of study.
"A good example is the 100-square board. You used to see them in lower primary, then upper primary, and now we've got them in the secondary school. Teachers on the project have discovered that they motivate the kids and they can do quite advanced arithmetic on them."
Crucially, the teachers have learnt that the resource lends itself to making pupils explicitly aware of learning expectations at every level, which is a key element of formative assessment.
CPD gained through observation, co-operative teaching and in-service training delivered by colleagues is highly effective, says Ms Kirkwood.
"It's classroom based and you see exactly how the teacher manages the lesson and the work children are producing.
"Teachers like learning from other teachers."