Yes, but not exactly in the way that the film implies. Titanic history tells us that gates did exist which barred the third class passengers from the other passengers. However, these gates weren't in place to stop a third class passenger from taking a first class passenger's seat on a lifeboat. Instead, the gates were in place as a regulatory measure to prevent the "less cleanly" third class passengers from transmitting diseases and infections to the others. This would save time when the ship arrived in New York, as only the third class passengers would need a health inspection.
At the time of the sinking, some stewards kept gates locked waiting for instructions, while others allowed women and children to the upper decks. As a result of poor communication from the upper decks, the dire reality of the situation was never conveyed. The crew failed to search for passengers in the cabins and common areas, and the fact that some third class passengers did not speak English, also presented a problem. As a result, many of the third class passengers were left to fend for themselves. Only 25 percent of the third class passengers survived the disaster.
I call extreme shenanigans on that. I think it's bull. What do you think?