I would think it would depends on the teacher's assessment?
My DS joins Tae Kwon Do (TKD) too. For one semester, he has to be held back in the same class even though he has acquired the blue belt because of his size. The teacher explained to me that the next class has bigger sized kids (will be a problem when they need to get a partner for sparring) and they will do exercises which would be more demanding. One boy (same age as DS) dropped out when he was promoted to the next class as he found that he couldn't do some of the actions and told his mom he wanted out .
I agreed with the master's suggestion then (as I see it as a lesson learned for her too...ie. the need to consider each child's promotion) . Now DS8 has progressed to the next class and he is happy.
