I believe the collection you are looking for may be The Other Side of Tomorrow, published 1973, editor Roger Elwood.
The stories you would be thinking of may be:
- "Let My People Go" by Joseph Green (see below)
- "Night of the Millennium" by Edward D. Hoch (previously asked and answered here)
- "The Speeders" by Arthur Tofte (previously asked and answered here)
In fact, there appear to have been two other questions (in Feb and Aug 2013) for this same collection, though neither has a formally-accepted answer.
"Let My People Go" does not appear to be available online but is described in an online review as:
[T]he story of the last few genetic throwbacks in a future of perfect
people. These normal children in a world of super-normals resort to
their only weapon -- emotional manipulation -- to win their freedom.
A different online review (from a blog called "My Reader's Block") provides summaries of all three stories:
"Let My People Go" by Joseph Green: In this story humanity has been
selecting for super intelligence. However there are always some
throwbacks born--"norms" as they are called. The norms are always at
a disadvantage, not just because of their lower intelligence quotient
but also because of the restrictions and discrimination that they
face. One norm, a poet, rises up as a voice for the oppressed and
becomes a Moses for his kind--asking "Pharaoh" (the government of the
su-norms) to build spaceships so he and his people can leave Earth and
have place where they can be free. Will the World Council agree? Or
will the norms be second-class citizens forever?
and
"Night of the Millennium" by Edward D. Hoch: As the world prepares to
celebrate the onset of the 2000s, a young man faces decisions about
his career choice. As he tries to decide between becoming a laser
surgeon like his father or a high-paying, high-profile job in
communication engineering. The man who is trying to recruit him gets
caught up in a plot to cause a revolt at the millennium celebrations
and Tommy (the young man) comes to his rescue....this causes Tommy to
think about a third career choice.
and
"The Speeders" by Arthur Tofte: In the world of the future, the
government has supposedly ensured that vehicles will be safe--no
speeding and no accidents. But there are always the young joyriders
who will find their way around the laws and restrictions. These young
men find that when thy joyride and manage to break the speeding laws
one too many times that they are incarcerated--not in prison, but in
Traverse Park. In what seems like a speed-demon's paradise, all bets
are off. The speeders can go as fast as they want and drive as
recklessly as they want. Is it really the freedom from restrictions
that it appears? Or is there a more chilling motive behind the
speeder's park?
Other questions about this collection have also referred to the following stories (these summaries also from "My Reader's Block"):
"The Others" by J. Hunter Holly: Emelen and his friends have a very
small world. They are restricted to four walled areas and are
instructed by the Voice. The Voice teaches them everything they need
to know and tells them exactly what to do and when to do it. But
Emelen is curious--where does the food they eat come from? How did
they get where they are? Why do all of his friends look different
(different number of hands or eyes or mouths or legs...etc)? One day
he discovers the Others and the world changes. Emelen finds a way to
get a whole new world for his friends--and all the people who are like
him.
and
"A Bowl of Biskies Makes a Growing Boy" by Raymond F. Jones: Probably
the darkest and most chilling of the stories. A young man who hopes
to be a biochemist one day makes a disturbing discovery about the
additives in his morning breakfast cereal...and just about every other
food item in his family's pantry. He soon realizes that the chemicals
have been added to allow the population to be controlled. Those in
power can't afford for him (and others who have discovered various
other means of controlling the public--from subliminal messages to a
secret organization that runs everything) to follow up on his
knowledge and so he is quarantined with the other "troublemakers."
But what will be his fate?