What federal limit are you referencing? Federally funded Early Head Start classes serving students under 36 months old must have two teachers with no more than 8 children (4:1 ratio). CFR 1302.21(b)(2). Kids in diapers will probably be under 36 months.
Many states have their own requirements.
Got it, thanks. Looks about the same, for what it’s worth: recommended ratio for children 13-35 months old is 4:1.