Where a child charged summarily before the sheriff with an offence pleads guilty to, or is found guilty of, that offence the sheriff may order the child to be committed for such period not exceeding two years as may be specified in the order to such a place as the Secretary of State may direct for the purpose of undergoing residential training, and where such an order is made the child shall during that period be liable to be detained in that place subject to such conditions as the Secretary of State may direct.