The first schools to teach in Welsh catered for children in areas where Welsh was the first language. A private Welsh medium primary school was established in Aberystwyth in 1939, but the first to be supported by public funding was opened in 1947 in Llanelli. The first Welsh medium secondary school was Ysgol Glan Clwyd in North Wales, opened in 1956, initially at Rhyl and then at St Asaph.
However, by the 1960s, increasing numbers of pupils in Welsh-medium education came from non-Welsh speaking homes - people sent their children there because it was believed that these schools achieved higher performance levels in examinations.
In 1988, the Education Reform Act gave Welsh the status of a core subject of the National Curriculum in Wales in predominantly Welsh speaking and bilingual schools, and the status of a foundation subject in the rest of the schools in Wales.
How are things taught?
Most Welsh medium secondary schools teach the majority of subjects through the medium of Welsh (i.e. lessons are delivered in Welsh), or bilingually, using both English and Welsh.
Support for Welsh language teaching is provided by a national team of mobile teachers called Athrawon Bro. They travel from school to school to support teachers and pupils in learning Welsh, and learning through Welsh.
Maths and science
Most Welsh medium schools teach maths and science in Welsh, but a few offer Maths and Science through the medium of English. There is a debate about this policy. Supporters of an all-Welsh medium curriculum claim superior examination success. Some teachers find the use of both Welsh and English works successfully. Others argue for science in particular to be taught in the language of most international scientific enquiry - English.
Typically, in Welsh speaking schools, English is introduced at age 7 for children from Welsh language homes. Generally, pupils learn quickly to read, write and use the language just as well as children from English language homes.
By the time your children are 10 or 11 years old, you should find your bilingual children have English language abilities similar to those of children who don't speak Welsh (i.e. who are 'mono-lingual').
It is rare for children in Welsh medium education to fall behind on English language competence. English is so dominant in the mass media and in streets and shops, that children tend to become fluent bilinguals - and have the advantage of two languages and cultures.