I bought a set on Taobao last year, and my daughter has been listening. The only inconvenience is that the video needs to be downloaded to the hard disk. And the volume is relatively large, so it is necessary to prepare hard disk space. Also, find a place with good network speed to download, otherwise the download time will be too long.

Taobao, search for "Mathematics Cui Li of Famous Schools", a complete set of junior high schools, about 100 yuan (or below), a full set of videos about 20-30G. My daughter has been listening to her class since grade one. Although the course may not be consistent with the local area (for example, plane rectangular coordinate system, some videos are knowledge points of junior high school, but we only learned them in Grade Two), the knowledge is basically the same.

You can Baidu it. There are some video clips. If you think it's good, it's not too late to buy it.