A few of school girls, especially under 20, sometimes utter such a word to male-friends for appealing that she is a feminine and qute, and so the expression has the opposite effect to what you intend.

As for your question, it sounds unusual to me. I have tutored many girls around your age but they never say "boku" even in conversation only among them. "わたし；watashi" is more natural. "あたし; atashi" is also natural but I personally feel that active girls may prefer this. Girls around your age may prefer this more than other generations. When I hear "boku" from girls, I imagine that they may like anime very much, especially boy characters and want to pretend like them. This is obviously in the minority but if you feel you are like that, you may want to use "boku". I looked up wikipedia about this topic, which is called "ボク少女; boku girls". The description there is roughly the same with what I mentioned after "When I hear "boku"..." Translation from wiki: According to a survey in 2009-2010, the ratio of junior high girls who use "boku" or "オレ; ore" is 1.2% and 3.8%. The total ratio including "じぶん; zibun" is 5.0%.

（私）あたくし or わたくし is more suitable diction to your intention. but somewhat adult-like and sounds like business person, just a caveat.