well, to start with, until he is safe to drive without a dual control car, you should not be out in traffic with him.
I did LOTS of driving with ds.
We went to a quiet street with no cars, and he practised one thing.
So, before he had any lessons, he spent time in a deserted street just learning how to move off from stationary.
Once he had a couple of lessons, we spent an hour just going round the block. Turn left, drive straight, turn left drive straight. Then turn right drive straight.
One skill, deserted road.
Then we added more in as he learnt it. We practised what he had learnt in his lesson.
The last thing we did was enter traffic.
If you do not have this sort of quiet street where you can drive without other cars, then... don't.
Ds only had 10 lesson because of all the practice we did in between. A huge amount of early driving is mastering the physical skill of the car, and only when that is comfortable to they pay enough attention to the road. So use your time with him to speed up the physical side, and let the instructor teach the road traffice side initially.
Once he was driving in traffic safely, he basically drove everywhere all the time. Every time I went out, he came too and drove short journeys, long journeys, round the block, to the shops. Every time we went to a car park he parked 4 or 5 timesbefore we went in to the shop, to practise parking.