@Wendy Chartier
Where did you get that bird from?.... Hatchery, private seller auction/swap?
If it is a true ISA brown (red sex link) from a hatchery then it could only be a pullet due to it's brown colour.... males would be mostly white. But that comb is very large for a 10 week pullet and those hackle feathers are starting to look pointed, so my guess would be that this is a second generation "ISA brown".... ie a bird that has been created by breeding an ISA brown hen to an ISA brown rooster, which means all bets are off as regards colour sexing and this is most likely a cockerel. The sex linkage to colour is a first generation characteristic only.
If it came from anywhere other than a hatchery it is almost certainly male.