This paper summarizes research findings which suggest that 6 to 11 year olds may be more vulnerable to environmental crises than younger or older youths. A survey of Moroccan immigrants in Israel and France found that those aged 6-ll at the time of immigration had a smaller percentage admitted to college than those aged 0-5 and 12 and over when they immigrated. The effect was identified as the vulnerable age phenomenon. It was hypothesized that while school transfers tend to be stressful for all youths, the fact is more likely to go unnoticed for grade school children whose problems would therefore command less attention from families. Replications with Canadian and United States data corroborated the finding and suggested, futhermore, that: (1) the effect was not specific to cohort, socioeconomic status, or language; (2) the effect was more prominent among interregional U.S. migrants than among shorter-distance migrants; (3) the effect was more noticeable among boys than among girls; and (4) the attrition effect of structural transitions between levels of the educational system should be distinguished from the vulnerable age effect. Certain developmental and environmental factors were presented as possible explanations for the vulnerability of youths in mid-childhood to social or school environmental change. (Author/MJL)