Why it is the common believe that Hispanics place less interest on academics than other ethnic group?

So are you asking why people believe this or why Hispanics
actually seem to place less emphasis on education?

I would
say that people believe Hispanics place less emphasis on education because they end up
being less educated than other ethnic groups.  For example, the link below says
that:

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Hispanics have a much higher high school drop-out
rate than do blacks or whites. Some 41% of Hispanic adults age 20 and older in the
United States do not have a regular high school diploma, compared with 23% of black
adults and 14% of white
adults.

This sort of
statistic might tend to make people think that Hispanics place less value on
education.

If you are asking why Hispanics have such bad
numbers in this area, there are a variety of possible factors.  One would be the
language barrier.  Blacks and whites, even if poor, do not typically speak a language
other than English at home.  This makes education easier for them.  It may also be that
many Hispanics end up having to drop out to work.  There are other possible factors, but
these are two of the more likely causes of low Hispanic educational
achievement.