New Mutants director Josh Boone has confirmed Omega Underground’s previous reporting of a July 10th production start in Boston via Instagram.

New Mutants will star Maisie Williams, Anya Taylor Joy, Blu Hunt, Henry Zaga, Charlie Heaton, and Alice Braga with a set release date of April 13th, 2018.
Production will take place in Boston and at the tail end of shooting will move to Montreal, which could mean characters from X-Men: Dark Phoenix might be appearing in New Mutants. Boone and Kinberg had teased James McAvoy‘s Xavier having a part to play in New Mutants.
SOURCE: JOSH BOONE