Improving the quality of teaching

Who’d have thought it? According to a research review (Kini & Podolsky, 2016), students’ academic performance & attendance correlate with their teachers’ years of teaching experience.
The effects are strongest within the first 2-3 years of experience, increase substantially in the following 7-8 years, & continue to increase significantly after that. 
The effect is particularly strong if teachers have stable positions & so have spent a number of years developing their skills in the same environment with similar courses & similar typical student profiles. 
Also, no surprises that a collegial, supportive working environment where teachers are encouraged to prepare together & collaborate has a strong effect. 
The review is based on research in the USA in the state education system but confirms what other researchers have found across many subjects in many countries, i.e. it’s reasonably generalisable.
For further examples of teacher efficacy studies as well as what tends to have the strongest effects on teacher continuing professional development, see the work of Professor Rob Coe: https://profcoe.net/
In conclusion, if you want to improve the quality of teaching at your academy, keep your teachers year-on-year & cultivate supportive working relationships with them & between them.

Reference

Kini, T., & Podolsky, A. (2016). Does Teaching Experience Increase Teacher Effectiveness? A Review of the Research. Learning Policy Institute. https://doi.org/10.54300/625.642