Don't know if this could be your John, but it is Andreas. The only other is a John A in Conchan, 7 years old. There are no 8-year-old Johns.
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1890 Census Andreas

RG12/4684
Registration district: Andreas
Sub registration district: C
ED, institution, or vessel: 1b
Folio: 63

John Teare, 32, General Labourer, Lezayre
Rebeca, 30, German
John W, 7, Andreas
Alfred L, 6, Andreas
Eliza A, 2, Andreas

Hope this helps,
Barbara