Continued professional development a better indicator of a good numeracy teacher than a qualification
The title says it all. A qualification is great... but it does not compare with ongoing professional development when it comes to improving tutor performance. This finding is consistent - from Li Ping Ma to Diana Coben to Bass, Ball and Hill.
For example, note this comment from Sheila Macrae, taken from Diana Coben's (2003) review of Adult Numeracy provision:
The findings also raised questions about the sort of mathematical knowledge needed by
teachers in order to be effective. Contrary perhaps to expectations, being a highly effective
teacher was not positively correlated with high levels of mathematical qualifications, a finding
supported, as noted above, by Begle’s research in the USA (Begle, 1979). Instead, the amount
of continuing professional development in mathematics education undertaken by teachers
was a better predictor of their effectiveness.
Here's my thought. Educators are in the business of educating. Therefore, an educator must be a master of learning, and that means commiting themselves to ongoing learning. Imagine being taught to drive by someone who didn't drive. There are things you can only learn about mathematics by actually learning mathematics.
Do note however, that the evidence does NOT diminish qualifications. A person with a qualification still outperforms one without (in general).
If you are teaching maths, the best thing you can do is to start to study. It will absolutely reinvigorate your teaching. It'll make you better, and it'll make your learners better.