The suppression of the indentation of the paragraph following
the heading is the default behaviour of the KOMA-Script classes, too.
Example:
\documentclass{scrartcl}
\usepackage{blindtext}% only for dummy text
\begin{document}
\section{Foo}
\Blindtext[2]
\section{Bar}
\Blindtext[2]
\end{document}

scrartcl
declares section
with the following code:
\DeclareSectionCommand[%
style=section,%
level=1,%
indent=\z@,%
beforeskip=-3.5ex \@plus -1ex \@minus -.2ex,%
afterskip=2.3ex \@plus.2ex,%
tocstyle=section,%
tocindent=0pt,%
tocnumwidth=1.5em%
]{section}
Note, afterindent
is not set explicitely. So the default afterindent=bysign
is active and the negative sign of beforeskip
supresses the indentation of the first paragraph following the heading. The vertical skip before the heading is still positive.
If you want to change the value of beforeskip
, you have to use the minus sign for its length , eg
\documentclass{scrartcl}
\usepackage{blindtext}% only for dummy text
\RedeclareSectionCommand[
beforeskip=-10ex plus -1ex minus -.2ex
]{section}
\begin{document}
\section{Foo}
\Blindtext[2]
\section{Bar}
\Blindtext[2]
\end{document}
Alternatively you can use a positive value for beforeskip
and change afterindent
to false
:
\documentclass{scrartcl}
\usepackage{blindtext}% only for dummy text
\RedeclareSectionCommand[
beforeskip=10ex plus 1ex minus .2ex,
afterindent=false
]{section}
\begin{document}
\section{Foo}
\Blindtext[2]
\section{Bar}
\Blindtext[2]
\end{document}
Both results in

Warning: If you only change afterindent
to true
or false
without changing beforeskip
to a positive value, the section
heading could overlap the text before it:

Code:
\documentclass{scrartcl}
\usepackage{blindtext}% only for dummy text
\RedeclareSectionCommand[
afterindent=false
]{section}
\begin{document}
\section{Foo}
\Blindtext[2]
\section{Bar}
\Blindtext[2]
\end{document}
beforeskip
for sections to a positive value?.