Flexibility training can be divisive issue. Even I'm divided on it. On the one hand, you can improve your flexibility levels to a degree through appropriate training (stretching) methods. On the other, the gains you can make are somewhat limited, and I'll often argue largely outweighed by the likelihood of injury (up to 80% of dance injuries are sustained during flexibility exercises. That's an awful lot.).
Having spent the better portion of my life in dance training and surrounded by other dancers, I can honestly say I've seen a LOT of time wasted on flexibility training for next to no gains. 85% of your flexibility is down to your skeletal structure, 5% is down to environmental circumstances, leaving only 10% down to muscular elasticity. 10%. All those hours spent trying to push that little bit further, and the best you can hope for is 10%.