From Changping how to get to Badaling ? Which site has cable car?

You must refer to the Changping suburb of Beijing. Well, it covers such a large area. If you tell me your specific location, I can help you more. Anyway, this is my general suggestion:
At Changping South Street bus stop, take bus no. Chang11 (昌11) to Hongnigou Station, where transfer to bus no. 919 to the wall section directly.

Similarly, I can just briefly help you. You can transfer from your current location by bus or MTR to Beijing South Train Station to take a bullet intercity train to Tianjin. Generally, it is dobale to return home from Tianjin. Don't worry!

Thanks Semma. We are Beijing Huijia School - station close to us is Nanshao.
It is helpful to know that MTR Beijing South Train station will take us bullet train and Tianjin.
thanks again.

At Nanshao MTR Station, take subway Changping line to Xierqi, where transfer to line 13 to get off at Xizhimen Station. Then you can transfer to line 2 to Jishuitan. Walk to Deshengmen then to take bus no. 919 or 880 to BDL wall directly.

Well, to BJ South Station, you can transfer at Xizhimen to subway line 4 to reach.