My son is year 3 UK, should he be targetting 2nd grade on the app?

Hi, my son is year 3 UK but the app doesn't make it clear what we should be looking at - either grade 2 or grade 3 (which i assume are US). It seems to equate Year 3 UK with Grade 3 US on the app, but just checking online Year 3 UK equates to Grade 2 US....can anyone shed some light please?

Thanks