Here is a template that you can use to convince your boss to support your professional development as a teacher.
Dear _____________,
Would you like me to improve as a teacher? Could you take a look at this new course by ESLinsider?
It's called TEKA.
It's a specialized course focused on how to teach English (especially to children). It's an interactive online course that has 18 topics, 60+ how-to videos (where I can learn by watching other teachers), and get feedback from the teacher trainer on assignments. The teacher said that he can even use our student books for those assignments.
This course would help me create lessons that are fun, interesting and engaging for students. Everything is learn-at-your-own-pace, so I can participate on my own schedule while still keeping up at work.
Here are some reviews by other teachers who have taken this course. One person said he saw a "massive improvement" in his student's behavior and that his students liked the activities a lot.
The cost is $299. Would your company be willing to reimburse me for this training?
Their website is here:
https://www.course.eslinsider.com/
This could be the professional development that I need to teach children.
Looking forward to your decision,
(Your name)