  In order to explore the nature of the 850 micron flux difference between
powerful radio galaxies and steep radio-spectrum quasars at z=1.5 reported by
Willott et al. (2002), we have observed 9 sources from their sample of 11
quasars at 1.25 mm. For 7 sources the 1.25 mm fluxes are much brighter than one
would expect from a purely thermal dust model fitted to the submm data,
providing evidence for the synchrotron nature of the observed 1.25 mm
radiation. If we extrapolate a power-law synchrotron spectrum to shorter
wavelengths, then for 6 of the 9 sources also the 850 micron fluxes are
dominated by synchrotron radiation. We discuss how far the (sub)-millimetre
data can be interpreted in accordance with the orientation-dependent unified
schemes for powerful radio galaxies and quasars. In this case the results
challenge the reported evidence for the receding torus model and for the
evolutionary trend of a declining dust luminosity with increasing projected
size of the radio lobes.
