In addition, you may be able to gauge your teen's work ethic by how well he or she handles homework, grades or sports practices. When teens want money, their work ethic may mature quickly.
3. A taste for instant gratification
If you notice that your teens spend every cent the minute they get it (whether from a job or from an allowance), they are likely not mature enough to handle a bank account or debit or credit card, Kay says.
"If they want what they want and they are constantly asking for more money from parents, they are not ready to manage their own money," says Kay.
Ulzheimer adds that silly or immature purchases -- particularly those made on a credit card -- are another sign of questionable financial instincts.
4. Can't or won't do the math
Kay says that if your teens do not possess the basic math skills or patience to learn to balance a checkbook, then they are likely not ready to handle most adult financial responsibilities.
"Managing money takes diligence and attention to detail, and above all, math skills," says Kay. "These are important skills your teen must acquire in order to manage their own money properly."
Improving your teen's money habits
If your teen displays one or more of the signs above, there is still hope.
As teens mature, their instincts toward money may improve. They may suddenly become interested in getting a job, saving up for something or making wiser buying decisions. You can help by encouraging these signs of financial growth as much as possible.
Kay suggests starting small by giving your teen a set amount of money for a simple task, such as a school supply budget, monthly entertainment budget or fall clothing budget, depending on what you think they can handle. Talk with your teen about what needs to go into that budget.