Śri Krishna Pattabhi Jois
Yoga is not competitive! However how hard it is to resist temptation.
Practicing in a room full of advanced students can affect an intermediate or beginner practitioner on many levels. On a positive side there will be motivation and yes-this-is-possible aspect. On the other hand, a person who practices with people on much higher level can feel down, rejected, find themselves losing self esteem and finally quitting the class. Sticking to continue the practice is important, as once you quit it is so hard to go back.
If that is your case, I would definitely advise to stay centred, moving your awareness inwards, see how you feel in a pose or in an attempt at a pose. Remember this is your practice and you are benefiting from it as much as the person next to you. See how week after week you can go further into a pose and watch your body accepting it. See if you are discovering new sensations in asana you have already done so many times. Rediscovery is one of the milestones in your practice.
Never compare yourselves to others. Everybody is different and it is all a personal and very private experience.
Focus on your breathing, listen to other people breathing and let their breath remind you of your own. It is such a blessing to practice in a group! Use the energy in the room, the vibrations created by the yoga flow for your own benefit. Have you ever noticed how different the room feels before and after the class? It is like in a sage smudged house, isn't it?
By all means: watch and enjoy your progress, do not control it and see what happens next...