Tax office & schools

Probably been answered here more than once but since my searches never seem to produce results here are the questions again.

Why should I build these buildings when they produce the opposite effect than their purpose. That is the tax office seems to reduce city income and the school significantly drops the city's science.

I'm sure there is something I am not taking into consideration but seems to me I would be better off if I don't build them. :confused:

Buck