I believe it’s becoming harder and harder to recruit new teachers and to hold on to the good ones (and that’s a rant for another day…) so this might be a lovely idea but possibly unrealisable practically. BUT
I do believe the Welsh curriculum is due for a revamp soon that could result in far more subjects being taught through the medium of Welsh. (As in, that was the idea that was put to the government, who have said they will implement it … but I’ll reserve judgement until they issue some sort of solid proposal.) The idea may well founder because of (1).
It would help, however, one of the beautiful things about first language families is that they tend to have a fluent grasp of two languages. So to me that would be a later battleground. I do know children who struggle in English because they are from first language families, however, I know far far far more who excel academically beyond the level of their monoglot counterparts.
My fiancée was taught English by a non-Welsh speaker. She went to Ysgol Glantaf in Cardiff.
It would be beautiful to see more Welsh speaking teachers. However, as Sara says, the challenge to recruit and keep teachers is hard enough in a pool of 4 countries. To limit is to 20% of one…logistics!
Cardiff plan to build 10 new Welsh schools (primary) over the next 5 years. There are 3 Welsh secondary schools in Cardiff and one in Barry. This will go a very long way to improve the number of speakers in the city. As Sara has said before, she lives in an area with a vibrant Welsh community. Plus, the area next to hers (Treganna) has an excellent Welsh primary school. Hence why my fiancée and I are looking to buy there.
There is a lot of support for teachers to learn Welsh and use bilingual elements in lessons but it’s not well taken up even so. Sgiliaith do a lot of work in this area.