I get the bus with my children to school in the mornings, this bus is usually very packed, no seats at all downstairs, there is upstairs but I don’t like going upstairs as I get dizzy and it’s not a long enough journey for me to bother the bus is usually moving as well when you go up , however my children want to go up and standing downstairs means they can often get in the way when there is nowhere to sit, so they prefer to go up, oldest is 10 sensible and in year 6 so secondary next year, what age would you allow a younger child to go up with him just the two of them whilst you stand downstairs?