When I was in high school I attended a marriage function of one of my relatives. I was in 7th class. Almost there were 5 boys of my age in that gathering. A relative of ours who attended the function conducted a competition for all the 6 of us. Each boy has to recite as many poems as he can and the boy who recites the highest number of poems without any mistakes will be the best and he will be the winner. I am lucky I recited more poems than all the other 5 boys.
Like this, we can assess the talent of the school-going children by asking questions relevant to them now and then.
We can assess the kids by asking simple but tricky questions in mathematics, English and other subjects also.