Students teaching tally marks

As promised, I am working on students creating more and not working on so many learning apps.
On the 8th day of school with only two days of tally mark instruction and practice, the students created their own videos (using Educreations) teaching their friends about tally marks.

Student A teaching tally marks

Instruction began with a pre assessment about tally marks. Only one child really demonstrated that they had any previous background with tally marks. There was a mini-lesson about tally marks. Students worked on educreations (used as slates) to make tally mark that was stated by the teacher. On the second day of instruction, students played a dice roll tally game (EM). Homework on the second day was to teach your parents how to do tally marks with a reminder to use their words and the number 1-10 listed on a page. All students brought the page back with the correct tally marks listed on the page. On the third day, the created these videos. This homework was handed out as a reference for the students. I do not believe students used it though (or I didn't see any of them use it).

This is also a great opportunity for me to assess their knowledge of tally marks.

For student A--this child wrote 3 as a reversal and 4 and 9 incorrectly. The student incorrectly wrote 10 tally marks wrong. I can see how they made their mistakes through the video. If it was a pencil-paper task, I know that it is just incorrect but not what they did and how they counted the tally marks.
I am also sending the links to their parents.

Student B teaching tally marks

For student B--this child wrote no corresponding numbers, just tally marks. It is very jumbled but you can clearly see that he is making the tally marks correctly and even has to redo 6 as he makes 6 marks and forgets to cross the 5 and then fixes it. Obviously, we can work on the "jumbled" tally marks but he clearly understands how to make tally marks to 10.

Student C teaching tally marks

For student C--one can quickly see the child's error for numbers 6-9. This is a short mini lesson to fix. Interestingly, this is the one child that has previous knowledge of tally marks. Did my mini lesson give him this misunderstanding?