Everything is easily accomplished in 6 steps ...
Create your own progress report and add skills to it. Choose a default scoring scale for your report, to allow trainers to set a grade. If you have created a progress report in the past, you can change it. Or make a copy, so your changes wont influence the existing reports.
After you've create a progress report, you can setup your training group. Select a report to use, you can create more groups if you like.
Now you can add pupil to your group. Just type their name and add them to the group, but if you want to enable them to see their own report, then use their email address instead of their name. If theirs an account with the address you specify, they'll receive an invite right away. When no account could be found, you'll get the option to send an email invitation. After the pupil is added to the group, you can add at most two additional email addresses to invite parents/guardians. To allow them access to the pupil's report.
Now you can start filling the reports for all of your pupils in the group, by using the selected scale you can give a grade for how well they perform.
In case you used an email address of a pupil and they accepted yout invitation, they'll be able to see their own report. The same goes for all other people (parents/guardians/(girl)friend) you've invited.
Do you train with multiple trainers or are you just managing the groups for your club or organisation? You can add other trainers to your groups, this will allow them to update the reports for all pupils in the group. Just add them by their email address.