But he was "surprised by how kind Welsh people were," says Dylan Parry, deputy head of Ysgol Bethel, near Caernarfon.
He was also amazed by the class sizes. At Mr Mosalemane's school, there are more than 400 pupils aged 7 to 16 - and 10 teachers. The computers and white boards were a shock too. At his school, five hours' drive south of the capital, Maseru, there is no electricity at all.
Ysgol Bethel's 150 pupils were also surprised by what he had to tell them, both in assembly and during question-and-answer sessions. These relatively affluent pupils, most driven to school every day, were shocked that Mr Mosalemane had a 30-minute walk to school. They also gained a new appreciation of their school lunches when told of the Lesotho equivalent: mostly boiled eggs, porridge and rice.
But, despite the obvious contrasts between a developed country and a very poor one, the teacher from Africa also found many common features between Wales and Lesotho. Both are small, mountainous countries, with their own language and traditions - and a love of choral singing.
It was these similarities that lay behind the decision to choose the tiny kingdom of Lesotho when Dolen Cymru (it means Welsh link), a charity set up in 1985, was seeking a developing country with which Wales could forge links.
Now, under the joint auspices of Dolen Cymru and the British Council, more than 50 schools in Wales are linked to schools in Lesotho. And a growing number of teacher exchanges is taking place with this former British protectorate, which is completely surrounded by South Africa.
Dylan Parry was delighted when Ysgol Bethel was accepted as one of a cluster of four schools in north-west Wales to form a partnership with schools in Lesotho -and when the "countless forms that took several weeks to perfect" resulted in a grant from the British Council of nearly pound;5,000.
But that sum has been nearly exhausted by flying four teachers over from Lesotho this autumn. Now he and his colleagues have to raise as much again to finance their return trip in February. Plans include a sponsored abseil down the Tower of Marquis on Anglesey to raise funds. They know it will be worth it.
Another project unique to Wales is one to boost Welsh language and culture in the Chubut province of Patagonia in Argentina. Funded by the Assembly and managed by the British Council, it has succeeded in attracting large numbers of Patagonians to Welsh language courses based in three centres, including one in the Andes.
The project, which started in 1997, sends three teachers a year to Argentina to teach Welsh and encourage social activities in the language and brings six Patagonians, identified as potential local tutors of the future, over to Wales for intensive language tuition.
There is nothing half-hearted about this boost to the spread of Welsh culture. Last month Rhodri Morgan, first minister for Wales, visited the annual eisteddfod, now held in Chubut at the end of October.
Linda Hall, assistant director at British Council Cymru, says of the project: "You can go all over the place to teach English, but Patagonia is the only place in the world you can go overseas to teach Welsh!"