IQ..Right or Wrong?

The definition of an IQ test is: standardized test that claims to measure an individuals intellectual ability.
The above video is a video I found on youtube that I thought was very helpful in my understanding of how accurate and reliable IQ testing is. When I was doing my practicum in my Grade 1 class, one of my students was given an IQ test and scored 50. The teacher was telling me that IQ rarely changes and that this child would struggle in school due to this score. By observing this child I did notice he did struggle in basic tasks that other students had mastered. He was also a year older than the other children in the class as he was held back in kindergarten. I feel that if this child was told that he got an IQ score of 50 and truly understood what this meant it would be detrimental to his learning and schooling life. By being told that you will struggle and not do well this child will have no motivation because he was told that it doesn't matter how hard he tries he will never be at the same level as the other children in his class. To me IQ testing is a way of labelling a child with a number that he or she is stuck with the rest of his or her life. Some children do struggle in school I don't believe they need a number to further discourage them from trying their best.