OP, city of Gaithersburg has most of those sports and some like soccer are multi season. Gaithersburg will place him on a team with other kids from the same school which is great for friendships and, as they get older, carpools . You really won’t find a single year round option, you will need to sign up for each season.
It’s also okay for your kid to not be sporty! I was not sporty as a kid and resented everyone’s focus on sports vs music or other pursuits. That said, it’s definitely helpful as an adult to have a bare clue as to how to dribble a basketball, hit a baseball, etc. so maybe introduce to lots of sports but then back off if your child does not really enjoy.

Rec league. At that age we did fall, winter, spring sports through our area rec league to give DD a taste of everything cheaply. When she was interested in something not offered by the league we’d sign up for a school with good cancellation policy.

For soccer just get your kid a ball and kick it around with him in the backyard or the park. Then sign him up for rec soccer and he will learn by playing and from the coaches. Rec sports
, especially for young kids, are generally for kids to learn sports. Everyone gets on a team and everyone has equal playing time.

DS is 9 and has been doing various rec sports since he was 5. You pick a sport for the fall and register your kid to play that sport, rinse and repeat for the winter and spring. DS has played baseball, volleyball, basketball, and soccer. You bounce around sports until your child finds something that they really like. DS also tried gymnastics and dance when he was 5.

I have no clue if there is a program that runs year round and changes out sports. Most year round programs are travel programs for one sport. If you want to expose your child to multiple sports you will need to register them for different sports. It isn’t that hard to do.

We definitely threw baseballs and dribbled and shot soccerballs and and took basketball shots at home.

As far as organized sports at this young age, MSI has a great kindergarten program for soccer, followed by first grade program next Fall - organized by school, so kids playing with schoolmates/friends. The county has Rec basketball in the winter. Look for it in November next year.

Can't speak to baseball. My kid played at that age and was miserable because none of the other kids knew what tney were doing and he was miserable.

At that age most people sign their kid up to play on teams doing rec sports through their local sports org. I don’t know what’s nearby to you, but t-ball, soccer, flag football are all great for K age. Kids find being on a team and playing games more fun then classes.

Swimming and tennis are year round, do those. You can do weekend tournaments/meets, or not. Look into the Y

Its unlikely to find something "year round", you'll need to sign up each season.
https://www.montgomerycountymd.gov/rec/activitiesandprograms/classes/sportsinstruction.html

Check out Coach Doug Seasonal Sports (ages 4-6)

When they are young, we signed them up for sports classes through the county. Usually they showed interest in sports their friends played (soccer, baseball) but as they got older they made their own choices/suggestions for new sports. Its great to get your kid off screens, but I wouldn't push a ton of sports if its not their thing. You may also want to look at martial arts, art classes, things like that.

They learn from us. We take them to a park and practice throwing baskets. We play catch. We go to batting cages. We got cheap racquets at Target or something like that and take them to a park with a cement wall and practice.

Call me maybe

I live in Gaithersburg, and where can I sign up my boy to learn sports, eg soccer, basketball, baseball. He is 6, a kindergartener.

I hate him to do hours of screentime on weekend, and I would rather send him out to do sports. DH does not take him to do any sports, and sometimes he is a bit bored with playground. I only can do kicking ball with him on the backyard. I have to give him a push, otherwise he would rather stay at home. I have a toddler that tag along, so there’s not much we can do altogether because toddler (super active, run and jump) wants to participate in “everything”.

I already sign him up with soccer, but it is only 5 session 1hr with MSI on weekend at spring. He is not competitive or sporty, a bit clumsy, and confidence low in sports. He is a geeky boy that likes coding game, drill on math and board game type. I already sign him up with summer camp with multi-sports/outdoorsy ones because he has no preferences/interests.

I want year round suggestions for weekend sport class, except summertime because probably he will be exhausted from outdoor camps.