Note that the e in te and the o in doceo are long since this course uses reconstructed Classical pronunciation: "Tē doceō".
In Classical Latin, C and K represented the same sound. C was used in native or inherited Latin words, while K was used to transcribe Greek words.
And by "doCeo", do you mean /tʃ/ or /s/?
That's Ecclesiastical Latin. In Classical Latin, all c's are pronkunced as k