It’s a tragic, and often preventable, summertime horror in Massachusetts: children drowning at beaches, lakes, or swimming pools. The toll during last week’s heat wave included a 13-year-old boy who died at Bell Pond in Worcester, the Globe reported.

On average, about two children in the United States drown every day. These heart-wrenching individual tragedies add up to a serious public health challenge.

Swimming lessons are among the more important safeguards. Free or low-cost lessons are available in many towns and cities, including Boston, but they aren’t always well publicized.

Here are some:

• The Boys and Girls Club offers free swim lessons to members at all skill levels. Membership is $25 for kids 6-12, or $5 for teens. Details at www.bgcb.org.

• The YMCA offers lessons for all age groups at 12 of its 13 pools across Greater Boston. Rates vary, and the organization offers scholarships. Check ymcaboston.org/swim.

• The City of Boston operates 18 pools and offers free swimming lessons during school vacations in February and April and low-cost lessons the rest of the year. More at Boston.Gov/BCYF.

Many other providers also offer swim classes. The message can’t be repeated often or loudly enough: Those programs can be a matter of life and death.