The Mathematical Association of America (MAA) is the largest mathematical society in the world that focuses on mathematics for students, faculty, professional mathematicians, and all who are interested in the mathematical sciences; that is, mathematics at the undergraduate level. Our members include university, college, and high school teachers; high school, undergraduate and graduate students; and others in academia, government, business, and industry. Our core interests are Education, Research, Professional Development, Public Policy, and Public Appreciation. The student web pages cover topics in academics, careers, research/summer opportunities, meetings for students, and more. If you are not yet a member, we urge you to consider joining and ask you to visit our membership page. As a member, you can help the MAA fulfill our goals to benefit you, the student.
For information about Dolciani Mathematics Enrichment Grants (DMEG), for projects designed to develop mathematical enrichment programs for talented students in middle school or high school, please click here.
Am I at the right place?
If you are a high school or middle school student thinking of majoring in mathematics, you have come to the right place.
If you are a high school or middle school student not thinking of majoring in mathematics, but you really enjoy math, you are still at the right place.
If you are a high school or middle school math teacher, possibly involved in your school's Math Club, you are also at the right place and we need your help.
What can I do at my school?
Hopefully, your school already has a math club or mathlete team. If they don't, try and start one. You may be surprised how quickly an organization can come together. A good place to start with some ideas on putting a math club together is at the Texas State University  San Marcos page on starting a club. UNC Charlotte has tips for recruiting members and running a club.
Mu Alpha Theta is a high school honor society for math students. Think about how cool it will be to graduate with a Mu Alpha Theta Honor Cord on your gown! Learn about what they do and how to set up a chapter in your school.
What can I do outside of my school?
The American Mathematics Competitions is a friendly problem contest sponsored by the MAA. There are five main competitions for high school students:

American Mathematics Contest 8 (AMC 8)

American Mathematics Contest 10 (AMC 10)

American Mathematics Contest 12 (AMC 12)

American Invitational Mathematics Examination (AIME)

United States of America Mathematical Olympiad (USAMO)
The overall goal is to use these contest to strengthen the mathematical capabilities of young people. Middle school students can also look at MathCounts.
Some areas have Math Circles. Here's a link to one in San Jose, CA. Ask around. Maybe if there isn't one, one can be started up.
What can I do in the summer to have fun with math?
There are a wide variety of summer programs available for talented high school math students. First off, take a look around you and talk to your teachers. There may be something going on at a campus near you. Otherwise, the following partial list of summer programs may help.

PROMYS (Programs in Math for Young Scientists)  PROMYS is a sixweek summer program at Boston University designed to encourage motivated high school students to explore the creative world of mathematics in a supportive community of peers, counselors, research mathematicians, and visiting scientists.

SUMaC (Stanford University Math Camp)  bringing mathematically talented and motivated highschool students from across the United States, and from around the world, to Stanford University for four weeks of serious mathematical pursuits.

MathCamp  A joint venture between the USA and Canada, this 5week summer program rotates to a different college campus each year.

Ross Mathematics Program  an intensive summer experience designed to encourage motivated precollege students to explore mathematics. During those eight weeks, students are immersed in a world of mathematical discovery.

HCSSiM (Hampshire College Summer Studies in Mathematics)  an intensive sixweek residential program for enthusiastic students. Working in small classes and individually, participants will actively engage in the process of mathematical thought.

SWIM (Summer Workshop in Mathematics)  a two week summer program at Princeton University for rising senior girls interested in mathematics.

MathILy (serious Mathematics Infused with Levity)  Do you want to explore and create mathematics? Consider MathILy, an intensive residential summer program that emphasizes mathematics that is pure but applicable and has a core curriculum of discrete mathematics.

HSMC (Mathworks Honors Summer Math Camp)  It is a sixweek immersive residential program held at Texas State University in San Marcos, Texas.
To find more summer opportunities, check the AMS list of Math Summer Camps or the AWM list of Other Programs.
Should I Major in Mathematics?
Actually, that's a question only you can answer. Some people have a passion for the intellectual challenge: solving difficult problems and proving conjectures are true. Others understand the versatility of a degree in math. If you decide to major in math, the question you will most be asked is, "What will you do with your degree, teach?" For many math majors, teaching is their goal. If you want to know what else is out there, take a look at the MAA Career Page.
A couple of statistics: In The Jobs Rated Almanac 1999, "mathematician" ranked #5 out of 250 job studied in terms of income, stress, physical demands, potential growth, job security, and work environment; The National Association of Colleges and Employers 2005 Salary Survery states that mathematicians earned a starting salary 37.7% above the national average. A 2009 study showed that the top three best jobs in terms of income and other factors were careers suited for math majors.
What classes are out there for a math major? Well, every math major takes a threesemester sequence in calculus. Afterwards there are classes in discrete math, differential equations, linear algebra, abstract algebra, and real analysis to take. Electives can include operations research, topology, cryptography, number theory, geometry, probabililty theory, statistics, and numerical analysis. Many school ask their students to do a senior research project or take a capstone course.
Outside of class in college, there are often MAA student chapters or math clubs. Some schools sponsor their students to take the Putnam Exam, administered by the MAA . Usually to get ready for the Putnam, prospective test takers go over past problems and discuss strategy at a weekly meeting. Faculty supervised student research is an exciting way to delve further into a topic you find exciting. Such work may be for college credit, or as an extracurricular activity. Researchers have plenty of opportunities to give a talk either at their home institution, at MAA Sectional Conferences, Regional Undergraduate Conferences, or at MathFest. Also, students can present their findings on a poster at the Joint Mathematics Meeting.