The uniform looks like its the same school they attended. There has to be some teachers with raised eyebrows that these two already bring back their kid to enroll.
P.S.
Just occurred to me why this is only his second year of work. I was like, first grader is 6 on average, so what were you doing during the first 4 years, Ryuuji? Then it hit me that he attends college (as Nana told him to keep the hairstyle to prevent any girls eyeing him during that time). And that'd mean after he graduate and found a job, they immediately have a second child right about then.
What we'll get first now, a third kid or a grandkid?
Time-wise, third kid is more plausible since Mana-chan will need 4 more years at the very least before she can have kid (first graders is 6 on average as said above, and for a very, very, early bloomers, girls can become fertile as early as 10 if I remember correctly). However, don't forget Mana-chan has marked Shou-kun to be her man, not just any random guy, so he will have to be an early bloomers too, to make it happen, so this brings the possibility of them having kid as early as 10-11 (grade 5-6) significantly lower. We can more realistically expect them to have kid as early as 14; so, with estimate of 8 years head start (or 4 years at the earliest possible), Ryuuji and Nana will likely have third (or even fourth) kid before they have grandkid,
if they so choose to.
If we see grandkid before third kid, no matter at which age Mana-chan bears that child, that can only mean Ryuuki and Nana were using contraceptive
or they didn't fu- (nah, that wouldn't be possible).