That's nonsense. About 30% get top grade in Maths. Very little get 87% on average.No. 3.5 (on the usual 4 scale) is typically half-way between a B and an A. The numerical value of an A,B,C,D,E varies depending on the school, but the lowest estimate of a B that I've seen would be ~75%. So figure halfway between a B and an A would be around 87%.
I'm on a another student forum, but the top grade in UK is first which is 70% or more. Only 30% get a first.
What percentage of US student get an A? I bet it isn't less than 5%. Which you are implying if you think halfway between a B and an A is 87%.
P.S. Another thing is US students are a year behind UK students.