The short answer is "anyone". Here are some examples :

Even toddlers on bikes with stabilisers can gain from off-road tuition in the basics of balancing, steering and braking and can learn to consider other path users and how to take care of their bike.

Children who are not old enough to take part in their school's Cycle Training Scheme but are keen to get going and perhaps ride out with their parents.

Children who have missed out on the opportunity to take part in a school Cycle Training Scheme or want to enhance what they have gained from that with more real road experience.

Adults who have never ridden a bike before, maybe are a bit embarrassed at needing to learn how to balance and start at the beginning, and perhaps want to keep up with their children!

Adults who used to ride but have lost confidence or are out of practice.

Adults who ride but never took any cycling instruction and know that their skills and road-craft are not really a match for today's traffic.

If you want to cycle you can do it!