Strade has the feel of a well-ordered grammar and offers only two English-taught subjects: maths and science. Both Tom's parents are English (one from Surrey, one from Shropshire) but, like many other incomers aware of standards of achievement in bilingual schools, they have opted for education in Welsh for him.
Tom has come into a biology lab to discuss coursework with Arnold James, the head of science. Like most teachers in bilingual schools, Mr James would prefer to go the whole hog. Tom has opted for science in Welsh but he admits that he speaks English to his friends outside lessons, even in school.
Welsh is, however, widely spoken in the school; it is the official language and often the social one too. Headteacher Geraint Roberts says it is so ingrained that it is difficult to shake the habit even when he asks pupils to speak English.
"If English parents have come to see me, their son or daughter continues to speak to me in Welsh and seems unable to break into English, even though they will never speak a word of Welsh at home," he says.
Children who go to Strade study Welsh as a core subject, equal to English in status and difficulty.
Mr Roberts admits that accommodating another core subject can increase pressure on his staff, but everyone is committed to the same ideal and he is proud that, unlike some Welsh-medium schools, Strade has maintained four option blocks. "Children need breadth," he says.
Llinos Priestland, the head of maths, would ideally like a bit more curriculum time, especially as one effect of having to offer maths in English as well as Welsh is that setting is less ability-based, she says.
Nevertheless, she is pleased that the school offers a wide choice.
She is also proud of the sell-out Welsh musicals for which the school regularly takes over the Grand Theatre in Swansea for three performances at a time.
Strade is one of three bilingual secondary schools in Carmarthenshire and has a wide catchment area. Its associated Welsh-medium primary in Llanelli is Ysgol Gymraeg Dewi Sant.
Children may go to a Category A primary such as Dewi Sant, where the first language is Welsh, but then choose to go to an English-medium secondary where they opt to study Welsh as a second language.
"They do Welsh as a first language at key stage 2 (from age seven to 11), then disappear at key stage 3," says Dyfrig Davies, Carmarthenshire's adviser for Welsh teaching. "It was a mistake to have two programmes of study when the national curriculum was introduced."
It is easy to see why this happens: key stage 3 tests (at the age of 14) are not compulsory when Welsh is a second language but first-language students can get an A* in the GCSE.
Pupils in Category B primaries are generally from English-speaking families but they are expected to be bilingual by the age of 11.
Lakefield Primary in Llanelli is a Category B school, where Welsh is a second language. Its head, Cardiff-born Peter Ayre, has learned the language and is now a passionate advocate of Welsh-medium teaching.
Ann May teaches a Year 5 class of nine-year-olds and, as a non-Welsh speaker, has been on several training courses. She is grateful for regular weekly help in teaching Welsh as a second language. Her support comes from Mary Rees, one of the five permanent peripatetic athrawon bro in Carmarthenshire, who provide back-up where needed. Today she is introducing the senses to Ms May's class, using a colourful poster. The lesson will be followed up during the week.
Virtually none of the children at Lakefield Primary speak Welsh at home and most will go on to the English-medium comprehensive school Coedcae.
Primary provision for teaching Welsh is generally deemed a success, while secondary provision still has some way to go. One key problem is that although it is compulsory for all children to follow a course of Welsh for 11 years, beginning at the age of five, the only compulsory exam is GCSE.
This means that when the new intake arrives at secondary school, teachers of Welsh as a second language have no indication of pupils' standards unless they make a specific effort to build relationships with the feeder primaries.
At Coedcae, where despite its "English" status 50 per cent of the staff speak Welsh to each other, headteacher Harvey Jones and his staff in the Welsh department, led by Eluned Rees, are well aware of the importance of making links with their feeder schools. Rhiannon Roberts is responsible for these.
"We began in 1989 by meeting the heads of the feeder schools," she says, "but I thought it would be more useful to go into Year 6 classes (the final primary year) and also to invite staff responsible for Welsh in the schools and the Year 6 teachers to come here. We have a workshop day in October and sometimes February as well. We invite the athrawon bro and the adviser."
The school has sessions on language teaching led by guests and has tried other links, including a webcam session when first-year secondary pupils answered questions put by Year 6s.
Ms Roberts takes a fast-paced oral lesson with Year 6 in each school, and on the basis of that (and consultation with the teacher) she assesses pupils for banding at Coedcae. She ensures continuity by encouraging use of the same reading scheme in the final year of primary and first year of secondary and by making laminated cards of helpful words and phrases for primary walls. The Welsh rooms at Coedcae are decorated similarly.
Welsh resources are gradually improving but many teachers still make their own.
WEIGHING UP THE OUTCOMES
* The number of Welsh speakers has increased, although the rise is probably among learners; there may be a decrease in numbers of first-language speakers.
* Bilingual speakers improve their career prospects, are likely to have an enhanced sense of their culture and have the opportunity to explore their own literature.
* It is generally agreed that bilingual people will be more interested in language generally and find the learning of new ones less problematic.
* There is some evidence that the learning of other languages is under pressure, although the evidence is difficult to quantify and advocates of Welsh point out that the take-up of foreign languages is poor in the UK generally.
* In those schools which are a half-way house, trying to introduce Welsh-medium teaching gradually, offering certain subjects in two languages can cause timetabling nightmares.