A pair of city councilors are pushing for the inclusion of all city children in a program that’s providing free admission to several of Boston’s cultural institutions to public school students and their families.

Councilors Erin Murphy and Ed Flynn filed a resolution order late last week requesting the council to support the expansion of the “BPS Sundays” pilot program to include the thousands of city children not enrolled in public schools.

Mayor Michelle Wu vowed during her State of the City in January to waive admission fees at various museums and institutions for BPS students and up to three family members on the first two Sundays of each month through at least August.

Two weeks in, “BPS Sundays” has drawn more than 2,500 families to Boston Children’s Museum, Institute of Contemporary Art, Museum of Fine Arts, Museum of Science, New England Aquarium and Franklin Park Zoo, officials have said.

At the same time, pressure to invite city children who either attend charter and parochial schools, the METCO program, or are homeschooled, into the program has mounted.

“There are over 20,000 Boston children who are enrolled in charter and parochial schools, and who attend the METCO program that should have access to the same wonderful opportunities as our BPS students,” Murphy said in a newsletter Saturday.

The program has caught the attention of MassGOP leadership, with party Chair Amy Carnevale calling the decision to exclude charter school students “politically motivated.”

“If Mayor Wu continues with the museum initiative, the Mayor should not exclude charter school students,” Carnevale said in a statement last week. “Just as families in non-charter school systems face financial struggles limiting access to these museums, so do many charter school families.”

Typically, tickets to the aquarium are $34 for adults and $25 for children, and tickets to the science museum are $29 for adults and $24 for children.

In the resolution order, Murphy and Flynn highlighted how the initiative is “using tax dollars to fund a large portion of the million dollar expense” and suggested a new name for the program, “Sundays For All.”

In a statement on the charter schools exclusion last week, a city spokesperson said the administration started with just the BPS community to “best understand how to engage community members and improve this program.”

“As we measure and learn, we hope to add more partners and resources to be able to expand the program even further,” the spokesperson said.