ImageMagick convert on a multiple files

I have 3 files in a directory:

aaa.jpg    
bbb.jpg  
ccc.jpg  

I can scale down an image using ImagkMagick convert:

convert aaa.jpg -resize 1200x900 aaa-small.jpg  

I want to do all the images in the directory, something like:

convert *.jpg -resize 1200x900 *-small.jpg  

but this results in files named like so:

*-small-0.jpg  
*-small-1.jpg  
*-small-2.jpg  

What I want is:

aaa-small.jpg  
bbb-small.jpg  
ccc-small.jpg  

How do I do this?

In a for loop it is possible to use the features described in man bash at

Parameter Expansion
...
  ${parameter%%word}
      Remove matching suffix pattern.  The word is expanded to produce a pattern just
      as in pathname expansion.  If the pattern matches  a  trailing portion  of the
      expanded  value of parameter, then the result of the expansion is the expanded
      value of parameter with the shortest matching pattern (the ``%'' case) or the
      longest matching pattern (the ``%%'' case) deleted.  If parameter is @ or *,
      the pattern removal operation is applied  to  each positional parameter in turn,
      and the expansion is the resultant list.  If parameter is an array variable
      subscripted with @ or *, the pattern removal operation is applied to each member
      of the array in turn, and the expansion is the resultant list.

The following one-liner should do the job

for f in ./*.jpg ; do convert "$f" -resize 1200x900 "${f%.jpg}-small.jpg" ; done

This works in bash, which is the standard shell of Ubuntu. I think it is easier to remember than the elegant method by Steeldriver (who uses only convert and no for construct).

mkdir small
for f in *.jpg ; do convert $f -resize 1200x900 small/$f ; done