... but not much slower.
The full grown adults who bullied me the last four years of High School were all remarkably genetically inferior people. They were on accelerated schedules because like monkeys they didn't have far to go. There was never much to develop there. I knew they reached adulthood earlier because ultimately the males were just life support systems for testicles and the females were breeder cows. You don't need very complex hardware to have sex, fight, brag and posture.
I knew at the age of 12 I was maturing at half the rate of humans in nearly all regards. I also knew despite still being intellectually adolescent I was lightyears ahead of every adult around me, much less the kids. As young as 12 I used to watch people's faces and think to myself "The left and right hemisphere are not doing much talking there. One of the reasons they have such high self-esteem is because their critical faculties are virtually nonexistent."
In a sane world truly concerned with healthy development of all children, Sapiens and Neanderthals would be segregated from kindergarten onwards into separate schools with no cross transfers possible unless physicians had determined their first diagnosis was wrong. If it became obvious a child was developing mostly as a Sapiens and exhibited all those typical behaviours they could be shuttled by a bus down the road and put back into population with their own kind. I hate to think about the smell at those Sapiens schools. There would probably be a lot of bloodshed and pointless killing but they'd be happy as a pig in slop amongst their own kind. When they came up for graduation they could be assigned simple manual labor jobs like plumbing, bricklaying or stuffing coloured rags into plastic bags for sale.
Keeping Sapiens out of tech, white collar and management would produce a 10,000 fold increase in innovation, productivity and general advancement. Three generations of this policy and the whole planet would look like "The Jetsons." The Neanderthal cells when they entered their college years would likely be doing prototypes for hoverboards and designing thorium reactors that would fit into a shoebox. Meanwhile up the street at Sapiens trade school ("ARBEIT MACHEN FREI" over the entrance) they would be having a contest lighting their own farts and trying to see how much broken glass they could swallow at one go.
ADDENDUM : The peak of the fake intelligence boom for a fake economy came in 2000. It will never return. The era when people with mediocre IQs (100-120) could attend college, learn Marxist doctrines but little else, then enter society with the proud stamp of "intellamajense" on their shirt sleeve and be guaranteed work in white collar professions will never return. The reason the boom and crash in information technology came around this time is that corporations were absolutely stuffed with people pretending to be competent with this tech before the bills started to come in. When this generation of actors had to produce the bubble exploded. The Y2K boondoggle helped enormously to generate demand for people who sounded right but could not do any meaningful work with computers. This whole era is now at an end. Increasingly people suspect college grads of being illiterate morons with no useful skills of any kind and they are rarely proven wrong. "Edjamafacashun" has gone the way of tulipomania.