This is guidance from an NHS organisation in Scotland:
www.centralsexualhealth.org/media/8009/guidance-for-schools-trans-gender-variance.pdf
I draw your attention in particular to page 14 on children with additional support needs:
Please note: by age 2 or 3, a child starts to develop a sense of being a male or female. Some children with a learning disability/additional support needs, however, may not develop gender awareness at the same age and stage as their peers. It is important that children with ASN are actively taught gender identity so that they understand the gender assigned to them at birth.
Conversely, this often requires blatant ‘boy/girl’ activities. However, once a child understands the gender assigned to them at birth, teaching and practice can diversify to include non-stereotypical approaches and allow the child to explore their True Gender identity.
So essentially two and three year olds with special needs should be engaged in activities based on sexist stereotypes until they understand what boys do (play with trainsets, rough-and-tumble games?) and what girls do (dress as pink princesses and play with dolls?). Once they understand what a girl is and what a boy is (circa about the 1950s), they can be encouraged to explore whether they really are a girl or a boy. If they don't fit nicely in with the stereotypes of their sex, they'll be on a path to social transition, puberty blockers, hormones and surgery.