Spring school holidays 2023

Hi,

I'll be visiting Japan over the period of March and April next year (2023) and want to visit Universal Studios Japan.

I'd like to ask when does the Spring school holidays start and end for 2023 as I believe the crowds at USJ during this period will be more busy based on theme park crowd predictors for periods pre-2020.

Japan Guide mentions it begins in the second half of March until early April but that's a bit vague given March spans across 5 calendar weeks for 2023. Would I be correct to say the Spring school holidays begin on 18 March and end on 9 April?
https://www.japan-guide.com/e/e2273.html

Yes, roughly so. School holidays are different for each school, grade and more so for each region. And term exams would start before holidays, allowing students to go home earlier in the day. Additionally, graduates would be out of school earlier, and university students have much much longer holidays.

Just for reference, here is an example of a crowd-predicting site. For March and April, look at the calendar that says 2023年 3月 and 2023年 4月 respectively.
https://usjreal.asumirai.info/monthly/6month-expect.html#i-6

Here are the colors that represent the degree of the crowd. A represents the least amount of people, predicting an average of 30 minutes waiting time for popular attractions. S represents the most, with 160 minutes waiting time.
https://usjreal.asumirai.info/monthly/6month-expect.html#i-2