The content specialists who were best able to reach both extremes were usually those with the deepest grasp of their content. One of the best math teachers I know has a proven track record with both students with severe impairments in math, and with students documented at +2SD in math (I happen to have been the one documenting both the -2SD and the +2SD, which is why I know the degree with certainty).
I have long believed quite strongly that there is an incredible need for the very best teachers to be teaching the "weakest" students. It is very common here for the "best" teacher to teach only the senior years and if in lower grades, then only the top class in a lower grade, especially for math which is often the only "streamed" subject. There is such a need for struggling students to have a teacher who knows their content deeply and LOVES it. And gifted students equally deserve someone who can take them further. This should not be an either/or scenario where the best teacher teaches the strongest or the weakest students.
Twice exceptional students not only need the depth of knowledge and the passion for the subject, but also someone who can apply that and figure out what causes a gap between apparent understanding and outcomes.
Having had a child who was very able in math (though far from PG) but also significantly 2E I watched them fly when they had excellent math teachers, and literally go backwards with a ho-hum teacher. The last two years of primary school they had two years of being taught math by a secondary math specialist (I am not sure why this teacher was in a primary school, his only student facing time was yr 6&7 math). My child's yr7 nationally normed test scores indicated just how well they'd thrived on having a great teacher. Our national testing happens about 1/3 of the way through the year, every two years. Two years later (so after a 2.5 more terms with the great teacher and 5.5 terms at a new school having started highschool) their math scores had not just not progressed, they literally went backwards compared to their own previous scores. They were worse off than two years earlier by every possibly measure.
When presented with this direct evidence the school shrugged and said "Well we don't see that in class." But they also continued to keep our child in the most basic math group that was not extremely "remedial" and never addressed the on-going gap between class participation and test results. Class placement was of course dependent on test scores, so a child who loved math, but could not perform, remained in a class with disinterested and struggling students with a very average teacher.
I was the one who eventually realised it was dyslexic reading errors holding them back, and that they needed coaching and re-enforcement on reading the questions and using highlighters. Their school never seemed to appreciate the weight of this issue or encourage the accommodations from their end.
They moved schools in mid yr10, at the new school they had the head of math teaching them for the remainder of their schooling. They very nearly chose HL math (IB diploma). I am fairly sure that had they had experienced continuous high quality math teaching (AND commitment to debugging of gaps between understanding and performance) they probably would have proceeded with HL. Staying on the HL path until literally the last possible moment certainly was extremely beneficial to their outcomes in SL math. Fitting into, and succeeding, in the most rigorous math class in the school required a teacher that knew HOW to work with this child, and wanted to.
The first highschool did not offer HL math, arguing they did not have any students who "needed" the option. Contrast that with a teacher that argues that "I think everyone should do HL math because it's SO EXCITING. It really is such an exciting course, this is where we really KNOW that we are mathematicians!!!... But if you start HL math and realise that it's taking too much time, because it does take more time, and you need to prioritize other subjects for the path you've now chosen, then you can step back to SL. The bonus is that you'll do even better than you would have without all that HL experience."
There is no failure here. There is only "It's ok to have other priorities". This is the attitude, and the work, of a teacher who LOVES their subject, knows their subject, and who gets the very best out of every child, but with compassion and emotional intelligence. Not everyone did sign up for HL math and go through this decision making process, but many did. My child was the last to choose SL instead, regardless of whenever each child who changed made that choice, I don't think any regretted the path.
