I would take my child out of that school - actually taking a child out of school is pretty harsh on the child - so fisrt it would become necessary to take the issue up with the teacher (blatant anti-male sexism here, i'd give this teacher a piece of my mind) then push to the head and board if necessary. Oh and perhaps legal action, most public bodies have a legal responcibility to avoid sexism, and that is what this is.
All of the 'differences' between men and women are just smoke - yes they are different, but we have more in common than our differences (at least biologically) the biggest differences are cultural, and sexism like this helps perpetuate these differences.
What i'm saying is, yes men tend to be stronger than women (testosterone makes it easier to build muscle, i think) but there are women who happen to be stronger than a majority of men (they are mostly weight-lifters) and there are men who are weaker than the majority of women.
Same with height, maybe it is more obviously with height, men tend to be taller, but you can SEE the cross over in height any time you sort a group of human by height. JUST like between black and white skinned humans, there is more in common, more cross-over than there are differences.
The assumption is like making a bet that some 5'10" person is a particular gender based only on their height - this doesn't define them.
The only defining quality that is predictive is number of penises, and that doesn't even work for inter-sex or trans-gendered people. (because GUESS WHAT - the idea that there are two genders, male and female, is a first order approximation, it is a flawed assumption, it is the most basic way of looking at gender...)