Almost any keyboard keyer with some memory can be an excellent training tool for someone wanting to learn or teach Morse.
I built a keyboard keyer with memory several years ago. After using it for several years I donated it to my daughter-in-law who was involved with the scouts. It became a very popular item, helping several scouts get their Morse Code merit badge.
Thanks. I was just trying out G4FON's program, but it looks like 20 wpm is as slow as it gets. I was going to suggest to him that he learn CW once at a speed close to 20 rather than learn it at 5 and have to relearn it at a higher speed, but he has been practicing with a key and oscillator and I have no idea what speed he is at.
Over three decades ago I learned CW on a cartridge that plugged into the C-64. I think it was called "Morse Tutor". What I liked about it was it started with 4 characters and when it sent a character you were required to type it on the keyboard. The program kept track of my progress and it added a new character when you hit the correct passing rate written into the program. I think that's an easier method that typing 5 minutes of CW on paper and adding characters when you hit 90%. However, I've looked and looked for a program that emulates Morse Tutor but w/o success.