The second-language Welsh GCSE must be given more space on the timetable and become more relevant to pupils if standards are to improve, according to a teaching union.
Rebecca Williams, policy officer for Welsh-medium union UCAC, said the subject must become a more constructive use of pupils' time.
Her comments follow a report from the Assembly's cross-party enterprise and learning committee, which recommended that the Assembly government consider making the qualification a core subject alongside English, maths and science.
The committee heard evidence that some schools offer as little as 30 minutes' teaching time a week for the short-course version of the qualification, and that it is often taught by non-specialist teachers.
Ms Williams said: "There's a lot of evidence that the GCSE short course just doesn't do the job - (inspectorate) Estyn mentions it every year.
"We want everybody to have the opportunity to leave school being bilingual. To do that we need to make Welsh relevant; a living language. Pupils need to hear it in the school playground and corridors, not just the classroom."
The committee made 22 recommendations for the Assembly government, including increased investment in more varied language teaching materials and an intensive course to help post-16 pupils prepare for using the language in the work environment.
An Assembly government spokeswoman said it would consider the recommendations before proposing new initiatives.
"We want to ensure that our education system makes it possible for more learners of all ages to achieve a broader range of Welsh language skills, which will enable them to use the language in their personal lives, socially and in the workplace."