avoiding spring school holidays

Hi.
i what to travel to japan in the early april late may but iunderstand that this exactly the spring school holidays, what are the dates of the school holidays ? and it is recommaned to avoid arriving during this spring school? what date do you recommaned for april/march to avoid any crowding (or less crowding )
thanks
pascal

but iunderstand that this exactly the spring school holidays

No! Spring holidays are usually in the second half of March. April itself is not school holidays, although, popular cherry blossoms spots can get quite crowded.

what are the dates of the school holidays ?

Depends on the school and region. It is generally in the second half of March and first few days of April.

and it is recommaned to avoid arriving during this spring school?

No, I think it is not a major concern, although it depends on what you intend to do. If you want to go to theme parks and don't like crowds, then you might want to avoid school holidays, for example.

Golden Week is more likely to cause you problems as far as crowding and full trains/ accommodation. Golden Week is April 29th- May 5th

We were in Japan in mid to late May, and the kids were all over the place. Many many school tours. But it was delightful! The kids were noisy but polite and fun to be around. On several occasions a few of the kids had an assignment to interview foreign kids and our grand daughter was a target. She loved it and acquired a couple of pen pals. I wouldn't necessarily seek out school groups, but don't worry about them.