Technological improvements are still being made. Choose new performance and convenience, not new gimmickry or styling that is just new casing around old brains. On the whole, the more you pay the more you get, but young children do not need much. Till a perfect school calculator is built there will have to be 'trade-offs ', for example, a well placed negative sign may not be available on the same machine as rounding off recurring decimals. When in doubt ask the child 's teacher what he or she prefers.