Urinating Cat Behaviors

Hi, we just adopted a 2 year old male tabby from the local shelter about a month ago and recently we've been having problems with him taking turns urinating on every bed. He does use his litter box, we feed him a mix of three different types of kibbles. Hills T/D, Science diet and Acana prarie. The science diet came with him so we thought we should just finish it, and the T/D the vet recommended for his minor gingivitis. Maybe about 2 weeks ago he urinated on my roommates bed and we thought it was maybe because he was upset with him, but the next day he went and urinated on another roommates bed and 2 days later, he urinated on my bed. We caught him in the act, he sniffed around and when he found the perfect spot he sat down and peed. We scolded him and kept him off the beds for a few days and it stopped for about a week and just started up recently again. He still uses his litterbox, before he only peed when we were not there, these days he waits till we're asleep climbs on and pees then. We threw tin foil on all the beds when we're not home to keep him off it but I think he's getting used to it. We scoop out his litterbox 3 times a day and even though we're not home for 6-8 hours a day due to school work we still give him a lot of attention when we are. Is there any way we can teach him not to pee on the beds or any reason for this problem? Any advice please, we're students and washing our bedsheets and blankets 4 times a week in the middle of the night is a bit inconvinient.