Updated August 13, 2015.
The short answer: Most children are developmentally ready for swim lessons when they are about four years old. Prior to that, their brains and bodies are less able to coordinate the motions of swimming strokes, so putting them in lessons isn't very effective. It could even be frustrating for them to try to do something that's beyond their abilities.
The longer answer is that some kinds of swim lessons are okay and even helpful for kids under four years old.
Toddlers and preschoolers, ages one to three, can benefit from swim lessons that emphasize water adjustment, safety, and swimming readiness skills. Some small studies have shown that children this age who have formal swimming instruction are less likely to drown, although it is unclear exactly what type of lessons work best. So it's important to remember that swimming lessons are never a substitute for direct supervision anytime your young child is in or near water—even the bathtub.
For infants (6 months and up), toddlers, and young preschoolers, look for a class that follows American Red Cross and YMCA guidelines. The most important of these are:
- Instructors should have first aid/resuscitation certification.
- Parents should be in the pool with their children.
- Children should not be required or encouraged to submerge their heads underwater if they are hesitant to do so.
It's also helpful if instructors are experienced in working with small children, so they understand what is developmentally appropriate and what isn't.
Observe a class and see if the students seem like they are having fun. Are they playing games and singing songs? Are they allowed to play with toys?
When enrolling older children in swim lessons, also look for safety-certified instructors and for a progressive program that allows kids to advance through each level as they master new skills. Again, see if you can observe a class. How does the instructor handle kids who are nervous, or who might be misbehaving? Are kids active most of the time, or spending a lot of class time sitting on the sidelines waiting for their turn? You want to see a good mix of instruction and games that kids respond well to, plus attention to safety. (Watch a video about how to choose swim lessons.)
Helping your child learn how to swim can keep him safer when he's around water. Swimming is also a great workout (and a lifetime sport). If your child joins a club or team, swimming offers both an individual and team sports experience.
Sources:
American Academy of Pediatrics Policy Statement. Swimming Programs for Infants and Toddlers. Pediatrics Vol. 105 No. 4 April 2000, pp. 868-870 (reaffirmed October 1, 2004).
Policy Statement: Prevention of Drowning. American Academy of Pediatrics Committee on Injury, Violence, and Poison. Pediatrics DOI: 10.1542/peds.2010-1264, published online May 24, 2010.