When schools went remote this spring, Katherine Riley heard from her students — not about their coursework, but their fears that their internet service was too slow to support video, or that they were using too much data on their phone plans.

Internet is now among the “basic necessities,” said Riley, a history teacher at Mariana Bracetti Academy Charter School. She said the pandemic had made inequities around online access “more apparent than ever.”

She was among the teachers, parents, and advocates on Monday who faulted Comcast Corp. for problems city students have faced participating in virtual learning during the coronavirus outbreak — and protested outside the internet and cable giant’s Center City headquarters, demanding it do more to ensure that all children can get online when school resumes.

Holding signs reading “Internet is essential” and chanting, “Comcast has a tower but the people have the power,” about 200 people attended the rally, organized by groups including the Movement Alliance Project, the Party for Socialism and Liberation, and the Caucus of Working Educators. Organizers attempted to deliver letters to Comcast CEO Brian Roberts but were blocked by police from entering the building.

The union representing Philadelphia school principals is planning to rally for free internet for all city students Wednesday.

Protesters’ demands come as the Philadelphia School District plans to begin the school year virtually, after a spring in which thousands of city students struggled to participate in remote learning, in part due to lack of internet access.

More than 21,500 Philadelphia children do not have an internet subscription, according to census estimates. Survey data from the School District — which enrolls about 125,000 students — point to a potentially wider gap: In 2019, only 45% of students in grades three through five accessed the internet from a computer at home, compared with 56% in grades six through eight, and 58% for high school students.

Superintendent William R. Hite Jr. pledged last week that “every student who needs it” will have internet access this fall. He said city and district officials were working with internet service providers but did not give details.

Comcast spokespeople declined to comment on the record Monday. The company this spring offered 60 days of free internet service to new low-income customers through its Internet Essentials program — an offer it has extended through the end of the year — and also made network Xfinity WiFi hot spots at public places and small businesses free for everyone. Comcast charges $9.95 a month for the Internet Essentials program after the free period ends; other monthly internet packages run from $65 to $98.

The company told investors last week it has 600,000 customers nationwide who are either getting free internet service or are “high risk” — meaning they’re behind on their bills, but Comcast isn’t cutting off their service because of the pandemic.

In March, Roberts and his family donated $5 million for Chromebooks for district students.

But advocates argue Comcast needs to do more — and can afford to do so. “Brian Roberts has a $14.3 million condominium at the top of this tower,” said City Councilmember Helen Gym at Monday’s rally, before leading protesters in a chant calling Comcast “trash.”

Protesters — who called on Comcast to “fund Black futures” — demanded the company open residential WiFi hot spots for free access. They also want the company to increase speeds on its Internet Essentials program for low-income families, saying students can’t use online learning platforms with the levels currently provided.

Comcast has said the residential hot spots — generated by modems in peoples’ homes — are “not intended for broad, public use and are not engineered to support the high volume of users that our business and outdoor hot spots can handle.”

Makeba Walls-Robinson, a paraprofessional at West Philadelphia High School, said some families she works with don’t have any internet access, while “a lot of parents” are struggling with slow internet speeds.

“A lot of times, they’re being kicked off” of Google Classroom, she said.

While her daughters’ teachers at McCall Elementary in Society Hill, taught online classes after schools closed in the spring, students would often get disconnected and struggle to rejoin, said Kimberly Callahan, who pays for Comcast internet access but said her family was also challenged by slow speeds.

“You would see their square freeze … I would hear my kids saying, ‘Jonathan’s trying to get back into class,‘” said Callahan, who called the disruptions “an everyday occurrence.” After about two weeks, some students stopped trying to participate, she said.

Though teachers can plan engaging lessons, “there’s nothing that messes up the flow more than kids dropping out and dropping back in,” said Jessica Way, a teacher at Franklin Learning Center. “They’re messaging you … ‘I’m so sorry, the internet’s going back in and out.‘”

Staff writer Christian Hetrick contributed to this article.