The Koch method is based on exposing the student to full-speed Morse from day one. The first lesson starts with just two characters, played in full speed. The student must "copy" them (i.e. writing them down or typing them, like in this page). Once 90% of the characters are correctly "copied", the student can go move to the next lesson, where just one more character is added.
Hz tone
words per minute
% volume
Lesson
Click or touch any letter to see and listen the respective Morse code
c h a r
and type chars below, or
Press Start button
The Morse parameters are suggestions that happened to work well for me. You can play with parameters in this page or in the Web Morse player.
After lesson 39, there are two "post-training" or maintenance lessons that you can use to try different speeds, or just not to forget the Morse code. The option "Post-training: all chars" creates a lesson with all possible characters guaranteedly included, just like lesson 39. The option "Post-training: mostly letters" reduces the frequency of punctuation and numeric symbols to better represent the real-world frequency of characters.