  We present observations at 1.4 and 250 GHz of the $z\sim 5.7$ Ly$\alpha$
emitters (LAE) in the COSMOS field found by Murayama et al.. At 1.4 GHz there
are 99 LAEs in the lower noise regions of the radio field. We do not detect any
individual source down to 3$\sigma$ limits of $\sim 30\mu$Jy beam$^{-1}$ at 1.4
GHz, nor do we detect a source in a stacking analysis, to a 2$\sigma$ limit of
$2.5\mu$Jy beam$^{-1}$. At 250 GHz we do not detect any of the 10 LAEs that are
located within the central regions of the COSMOS field covered by MAMBO ($20'
\times 20'$) to a typical 2$\sigma$ limit of $S_{250} < 2$mJy. The radio data
imply that there are no low luminosity radio AGN with $L_{1.4} > 6\times
10^{24}$ W Hz$^{-1}$ in the LAE sample. The radio and millimeter observations
also rule out any highly obscured, extreme starbursts in the sample, ie. any
galaxies with massive star formation rates $> 1500$ M$_\odot$ year$^{-1}$ in
the full sample (based on the radio data), or 500 M$_\odot$ year$^{-1}$ for the
10% of the LAE sample that fall in the central MAMBO field. The stacking
analysis implies an upper limit to the mean massive star formation rate of
$\sim 100$ M$_\odot$ year$^{-1}$.
