Stop consonants after initial /s/ are standardly spelled as the unvoiced stops /p/, /t/, and /k/. Phonetically, however, they are similar to the voiced stops /b/, /d/, and /g/. Research suggests that many young children make consistent, reasonable, but unconventional, judgments about sounds and English spelling. This paper considers the case of the classification of stop consonants after initial /s/. The first experiment used a spelling test and a sound test. The spelling test asked 76 kindergarten and first-grade children what letters they used to spell the second sounds of syllables beginning with /s/-stop clusters. The sound test asked children to pronounce the syllables that remained when /s/ was deleted from syllables with initial /s/-stop clusters. This experiment found that some children consistently classify stops after /s/ as voiced. They spell /spo/ with B rather than P, and they state that /spo/ becomes /bo/ when s is deleted. Such nonstandard responses become less frequent as reading and spelling skills increase. In a second experiment, 24 university students were given spelling and sound tests that used the same lists of stimuli as Experiment 1. Experiment 2 confirmed that literate adults classify stops after /s/ as unvoiced, and that some adults are not very much aware of the phonetic similarity between stops after /s/ and voiced stops. (Author/AMH)