Get to the academy early. This allows the student to shake off any nervousness they may have. It also gives the child time to get into the right “headspace” to be able to start the class right
Teach your child how to tie up their belt. This is particularly challenging for the younger practitioner but with patience and in time they (you) can do it
Have zero expectations, correction, the only expectation to have is that the child is having fun. If they enjoy themselves, they will want to come back. The secret to getting good at Jiu-JItsu is to keep turning up.
Don't worry if your child is struggling or looking lost, this is part of the process. They need to work it out themselves, becoming involved from the outside of the class will at best distract them or worse create a negative feeling towards training.
Don’t compare your child with others, even siblings. Progression in JIu-jitsu can be very slow, but it is also inevitable. Improvements can be very minor and almost imperceptible to the outsider, but all these little improvements add up over time
Tell the instructor if there is anything that can affect the child's learning, especially developmental challenges. Children on the “spectrum” or with attention issues benefit greatly from Jiu-JItsu. Also let the instructors know if there is anything going on off the mats that could affect them on the mats. Likewise any external achievements that can be celebrated at the end of class, helping to reinforce positive behaviour
Ask them how their class went, but don't offer too much input. Get them to show you what they learnt, avoid correcting them even if it seems wrong. Just be interested in them. If you have any questions or concerns bring them up to the instructors, don't let time go by and not have a problem addressed.