I was out playing football with my boyfriend and his two mates when a bunch of kids about 11-13 years old came up to us and tried to steal our ball and were generally being idiots. We kinda let them play a bit then they went and sat down and I could hear them whispering to each other trying to guess what gender I was. I heard them say "Go ask her, or him, or THAT" the "that" bit was a little hurtful but I was happy that they thought I could be a boy. Then one kept saying to the other "go and ask" so I was waiting for it til my boyfriend came over and hugged me and they then assumed I was a lass. If they had actually asked me I dont know what I would of replied. If I said I was a boy it would be obvious i'm not coz of my voice. At least Im getting a little better at passing for a male lol.

I used to get called he/she all the time in high school, but I didn't mind, being called "that" is a little rude though. I have the same problem with my voice and it giving my birth gender away. You might be able to try voice training, try checking Google for something along those lines. Its nice to see you've got the support of your boyfriend.

Kids can be such lovely, heartless creatures.. At the same time, they did pull the 'go and ask' card which is more than most adults do; they simply observe, assume and conclude (and thats-that).

If you don't feel confident at this point to answer that question with 'I'm male, hear me roar... rawr', then I'd suggest a simple smile-and-nod or.. grin-and-nod.. or smirk-and-nod... or just go 'boo'. Or flex. Flexing is cool. 

Also, good stuff for the possible pass.

If you don't want to answer directly, there's always such responses as "Why do you want to know?", "What does it matter?" or "Mu".

Or you could non sequitur it instead .

"Are you male or female?"
"Peking cactus flavoured parking metre".