Computerization of school suggests a) ability to use computers, and b) application of computers as means of adaptive teaching. An attempt is made to consider both aspects from the same viewpoint - i. e. in connection with problems resulting from the psychological irreversibility of compression of imformation in semiotic and algorithmic processes. Optimistic expectations concerning positive influence of algorithms on mental development of pupils are questioned by the author; it is pointed out though that adaptive teaching may neutralize undesirable effects of the information compression (while inadequate ways of teaching how to use computers may aggravate them). Particular psychological, semiotic, and technical aspects of computerization of school are also considered and illustrated.