CharDegAgGroup( G [, q ] )
CharDegAgGroup  computes  the  degrees of irreducible   characters
of  the finite polycyclic group  G over the algebraic closed field of
characteristic q.  The default value for q is zero.
The degrees are returned as a list of pairs, the first entry  denoting a
degree,  and  the  second  denoting  its multiplicity.
    gap> g:= SolvableGroup( 24, 15 );
    S4
    gap> CharDegAgGroup( g );
    [ [ 1, 2 ], [ 2, 1 ], [ 3, 2 ] ]    # two linear characters, one of
                                        # degree 2, two of degree 3
    gap> CharDegAgGroup( g, 3 );
    [ [ 1, 2 ], [ 3, 2 ] ]
The algorithm bases on~Con90b. It works for all solvable groups.
GAP 3.4.4