It's all about selling yourself
This is in response to June's letter ('It can be tough to find teaching work', Postbox 23rd September 2019)
You need to lead with your success stories: what results you've gained for others. Blow your potential customers away with the successes you've achieved.
From what you've said, the old stereotypes are kicking in and people immediately think that you can't do what you claim to do, so you need to have them convinced before they get that far.
Try and get video testimonials from your students/students' parents. That way, you can have these on your website, or wherever, to pre-sell yourself and convince them that you're the teacher they need long before any prejudices the viewer may have kick-in.
Do a video sales letter-type of thing where you start with a presentation and your voice-over, that way they can hear you talking before they see you. Show your testimonials, your results, your achievements, and that way you may have them convinced before you segue into a head-and-shoulders video shot...
"Hey, bet this wasn't what you were expecting, right? [Laugh]
Ha, ha, I know, I get this ALL the time. Right up to the point when I deliver and, well... I've already shown you some of the results that students have achieved from working with me.
Here are a few more...
This is where video testimonials, preferably with you in them, as well (like a thumbnail with you in the corner chatting with your student) - that way they can't be discounted. Note: add them here before they get a chance to exit the video, you can go into your background for those still watching.
This is just a small sample from those who I've helped, though...
A little background... I was born in SE Asia, but I grew up in... and I've taught in <insert countries/places>... and I've helped <insert amount of students> achieve unparalled successes...
etc." And take it from there. Remove their objections BEFORE they get to the point where their prejudices engage. It won't work with everyone, but it might improve your success rate.
Russ