Does learning too many languages affect the learning ability of child in anyway especially Mandarin since it's quite hard to learn. I am not sure if my 4 yr old should learn Mandarin in school. Will it be too hectic for him to learn a difficult language along with all the homework ?

it is okay as long as your son have interest on it. kids learn faster then adults. maybe u thought it is tought for him but it is his learning process. unless u see his reputation didnt increase much and he is stress, then u should do something.. im ex chinese shcool students. and as far as i remember, i learn much from chinese friends since we communicate in Mandarin in school.. it just happen naturally. Fyi, my parents is not Mandarin speaker.