All MCF Cyclocross races for 2011 offer free entry to the junior categories. If you choose to race your USAC category (e.g. Cat 4), you are expected to pay the normal entry fee (typically $25), even if it is your second race at the same event.
Some race directors may offer free entry to juniors for any race, but the MCF guidelines are free entry only for the junior categories. This provides an incentive for all juniors to race together.
This applies to all CRY, Lazer, and non-series events.