The reality is in the UK you can't bring foreign under 18's to the UK. Just accept that is the LAW....want to smuggle and hoard 16 year old Brazillians then start a save in Spain.
Again, the problem is with FM not explaining things properly, and in REALITY, very, very, very few 16 year olds would sign pre contracts for 2 years later. Also now under Brexit (whether you like it or not is quite frankly not relvent), is that the vast majority of those kids would never get a work permit now anyway. Kids who are already here don't matter, and many will not get that work permit extended.