When were computers put into schools?

Good question - it all depends on what is meant by "small computer". It's safe to say that the computers of the 1950s were not small, as most of them filled large buildings. By the 1970's data processing computers had reduced to the size of large fridges, so they were certainly small by comparison. The end of the 70's saw a range of personal computers that could sit on a desk. The IBM PC was launched in 1981 / 1982 and was regarded as the first of the "professional" desktop computers although it didn't advance the technology to any great extent when it was launched. Backtracking a few years, microprocessors were developed in the 1960s in support of the NASA space program among other projeccts. The Apollo missions carried computers based on (I believe) the 6502 micro-processor, a computer chip about 2" long and 1/2" wide. the 6502 sported a staggering 64 Kbytes of memory (2 Gbyte in today's PCs is 32000 times as large) and ran at around 4MHz (modern PC's run about 500 times as fast and typically process 32 bits of data simultaneously compared to 8 bits for the 6502). Despite the meagre processing power, the 6502 and the competitive Z80 performed some incredibly powerful tasks and both processors can still be purchased today. My vote for the first "small computer" is the 1960s which saw the introduction of the 6502 and Z80.