Extending visitor visa with one on one Chinese lessons

Does anyone have any experience of extending a visitor visa with one on one Chinese lessons? I’m current enrolled in a group class at a university, but it’s expensive and not great. I have heard that it is possible to extend a visitor’s visa with six hours per week one on one study (which ends up being about the same price as the classes I’m doing). Guoyu Ribao or TLI were the options mentioned.
Is this just a rumour?
Can anyone tell me if they have done this?
:help:
Thanks